Asher Abid Khan sat in Istanbul's Ataturk Airport and considered his next move — forward to Syria and enlistment in the Islamic State, the militant group that had drawn him to the possibility of dying for Allah, or home to Texas and his bewildered family whose imploring messages were filling his voice mail.

The 19-year-old pulled out his phone and dialed.

"I want to come home," Khan told his father, Mohammed Abid Khan, who sat huddled in his living room here with his wife and other children.

Hours later, without ever leaving the airport, Khan boarded a plane and flew home to this Houston suburb.

His family had saved him from an uncertain fate in Syria, but not legal jeopardy in the United States.

Fifteen months later, in May 2015, the FBI charged Khan with conspiracy and attempting to provide material support to the Islamic State. Instead of life inside the caliphate, Kahn now faces up to 30 years in prison.

To his family and lawyer, Khan was a misguided and naive teen. Before flying to Turkey, in conversation with a friend on Facebook, according to court documents, Khan said: "I wana die as a Shaheed," using the Arabic word for martyr. And he was said he "looking forward to dying in Allah's cause and meeting Allah."

But his defense lawyer, Thomas Berg, said that Khan stepped back from an irrevocable decision and has since returned to a moderate path.

"He came home and did the right thing," Berg said. "If the government was smart, they would exploit that. My kid could go to the mosques and talk about redemption."

And, Berg said, if Khan is imprisoned, there is no incentive for the next young person having doubts about joining the Islamic State to turn around and come home. The government's approach, he said, leaves no way back.

Berg would not let a reporter talk with his client.

To the FBI, Khan is an unknown risk, and one that is best mitigated through prosecution. The case is emblematic of the American approach to confronting the Islamic State. While some European countries have decided to treat young radicals returning from Syria as prodigals in need of a deradicalization program of counseling, education and employment, the United States treats Islamic State recruits, even those who make it no further than an airport, as terrorism suspects.

Since the United States designated the Islamic State, also known as ISIS, as a terrorist organization in 2014, the FBI has made an arrest almost every week in connection with the group, many of them young people who were radicalized online. More than 60 people have been charged with material support and other charges. Twelve of them have pleaded guilty, including a 17-year-old from Virginia who was sentenced to 11 years in prison and a lifetime of supervised release and monitoring of his Internet activities.

FBI Director James Comey has called on Muslim families and religious leaders to work with the bureau to prevent young Americans from becoming radicalized, saying "our interests are aligned."

"We just need to make sure that folks are understanding that this is a problem that's everywhere and speaking up when they see something," Comey said earlier this year.

But Khan's case — and dozens more like it — is leaving some in the Muslim community with the impression that, for federal prosecutors and the FBI, there is no alternative to incarceration.

Mustafa Tameez, a community leader in Houston who has worked with the Departments of State and Homeland Security on countering violent extremism, said: "Nobody became a (special agent in charge) by giving a talk to parents about the dangers of getting recruited by a terrorist group. You make your bones by making a big arrest. We have to change the rewards system."

He said while some cases have to be prosecuted, the United States also has "to counter the extremist narrative and build capacity to protect these kids and keep them away from predators. We have to rethink our approach."

U.S. officials, who spoke on the condition of anonymity to discuss an ongoing investigation, said there are numerous cases in which agents have worked with families to prevent radicalization and criminal charges were avoided. The officials said there were indications — worrying, although not conclusive — that Khan had not shed his radical views after returning to the United States.

Khan told a friend months after he was back from Turkey to keep an open mind about the Islamic State, according to the FBI. The bureau also learned that concerns had surfaced at Khan's mosque, where he was teaching seventh grade Islamic studies on the weekend.

After Khan was arrested in May, M.J. Khan, of no relation to Khan, the president of the Islamic Society of Greater Houston received an email, which was provided to The Washington Post, from one of the mosque's religious leaders: "I was told that he has some ideological beliefs or sympathies towards certain groups that are unhealthy."

The FBI said that mosque members told agents that Khan believed that America was the "Dajjal" or the Great Deceiver.

But Imran Moton, the Sunday school principal, described Khan as a "perfect young kid" who followed an approved curriculum. He said nobody had ever said that Khan had expressed any sympathy for the Islamic State.

"Think of the these charges as insurance," said a senior U.S. law enforcement official, who spoke on the condition of anonymity because the case was ongoing, referring to Khan. "We don't know what he's going to do. This guy may be on the path to deradicalization. We err on the side of caution."

Asher Abid Khan's parents came to the United States from Pakistan more than two decades ago, following a well-worn trail to Texas that many Southeast Asian migrants had taken before them. They worked three jobs — at a gas station, Pizza Hut and Wal-Mart — to support their four children, all boys, who attended the local public schools. The Khan family prayed at Masjid Al Salam, a large and vibrant mosque that serves the area's approximately 400,000 Muslims, the largest community in the state.

Among Khan's friends at the mosque, as he neared graduation from high school, was a Mexican convert to Islam, Sixto Ramiro Garcia, who went by the name Abdullah Ali.

Together, Garcia and Khan began to watch radical videos online, according to court documents. Garcia posed with a black flag, later the symbol of the Islamic State, which a friend posted on Instagram.

Khan began to assert that women should be covered. At home, relations with his family became strained. He objected to his parents' decisions to work at businesses that sold alcohol.

In October 2013, a few months after graduating high school, Khan moved to Australia to live with his uncle's family in Sydney. Before leaving, in a Facebook message to an old high school friend, Mais Suied, he wrote, "I hope Allah gives you the best in this life and the next!"

Khan enrolled at the Australian Institute of Professional Education and got a job at a 7-Eleven convenience store in Sydney.

According to court records, he also joined Hizb ut-Tahrir, an international political organization that seeks to create an Islamic caliphate.

Khan began exploring the possibility of traveling to Syria. He felt his "brothers and sisters" were being "raped, tortured and killed," in Syria, according to court records.

He messaged Suied, an Iraqi whose family had moved in 2008 to Houston, according to Facebook messages reviewed by The Post:

"im thinking about going...do you know Abu Bakr al-Baghdadi?" he asked, in December 2013, referring to the leader of the Islamic State.

"Nope," replied Suied, 18.

Later, he asked her if a friend she mentioned is in the Islamic State.

"Nope, he's Shia'a lmao"

"Really?? LOL do you have anyone in ISIS," Khan asked.

"Yea all my ramadi people which is my vousins lol they all are crazy haha"

"Where is Isis do you know? Bc i might go early"

"In floja (Fallujah) I think." (Unsure emoticon) cuz all sunni lives there."

Suied said that Khan might have difficulty when he landed in Baghdad and suggested that Turkey might be a better entry point.

On Jan. 6, 2014, Khan contacted Garcia, 20, the Mexican convert, expressing his desire to go to Syria, according to court records. In Australia, Khan managed to get in touch with an Islamic State facilitator in Turkey named Mohammad, who had promised to get them across the border. In a message with another high school friend in the United States, who urged Khan to "wait a couple of years and see if [his] perspective changes," Khan said she needed to understand his feelings.

Maybe there is a "better way to help out," wrote the friend, Ifrah Farooq, back in Texas, but Khan was insistent.

On Feb. 23, Garcia flew to London from Houston while Khan took a flight from Australia to Malaysia the next day, with a later connection to Turkey.

When Khan landed in Kuala Lumpur, his parents had already learned from their Australian relatives that Khan was on the move, heading to the Turkish border with Syria. "We were scared," said Afroz, Khan's mother, in an interview.

The family left him a message saying his mother had been hospitalized — a lie, but one they hoped would turn him around.

"My parents are tipping bro," Khan said in a message to Garcia. "I hers my moms in the hospital."

"Dude, you can't pull (expletive) like that, I didn't come with that much cash, I have no connections I've got no clue, wtf," Garcia responded.

Khan promised to continue on to Turkey, but never hooked up with Garcia.

Once home, Khan didn't say anything about wanting to travel to the Islamic State.

"Never, never," his mother said. But Khan did eventually tell his parents that he never believed the story that his mother was sick.

Back in Houston, Kahn had slipped into a new routine, taking classes at the University of Houston and working at Pizza Hut as a delivery driver — without having drawn the attention of the FBI for his aborted trip to Syria. He was circumspect with friends about where he had been.

One friend, who spoke on the condition of anonymity because of the sensitivities surrounding the case, said when he returned he seemed less strident about following the tenets of Islam.

"It was a change for the better," the friend said.

Khan continued to follow Garcia on Facebook and receive updates from his friend. Garcia had messaged him almost immediately after Khan left Turkey that he had found the facilitator Mohammad in a border town called Antakya. An excited Khan emailed Farooq, according to court records and told her to keep Garcia in "your prayers."

Garcia had sent Khan photographs of himself, including one with an AK-47 rifle. "That's my baby," Garcia messaged shortly after he entered Syria. "You can have one too if you'd like."

In August 2014, when Garcia had joined the Islamic State, Khan cautioned: "make sure they are doing everything according to Islam you know, not killing innocent ppl and all that."

Garcia's absence had not gone unnoticed. Worried family members contacted the FBI, which opened an investigation.

By October 2014, the FBI finally unearthed Khan's connection to Garcia after obtaining a search warrant for the convert's Facebook account, and Khan was placed under surveillance.

The FBI also suspected that Khan, who had applied for another visa for Australia, might be considering another effort to reach Syria.

His friend Garcia was now believed dead; somebody had used his Facebook account to message his family that he had died as a martyr.

On the morning of May 25, 2015, Khan was arrested at his house.

"Why are you here? What did we do wrong?" his mother asked agents as they searched the house.

Kahn's attorney, Berg — a former colonel in the Army reserves, who has served at both Guantanamo Bay, where he helped set up the first military commissions, and in Afghanistan — dismissed the evidence against Khan as "a lot of talk and Facebook crap."

Khan's arrest had followed an attempted attack the same month on an event in Garland, Texas, where cartoonists drew the prophet Muhammad. His depiction is prohibited under Islam. The two attackers — Elton Simpson and Nadir Soofi of Phoenix — were killed by police.

The FBI had arrested Simpson in 2010, charging him with lying about his plans to travel overseas to fight in Somalia. But a judge sentenced him to probation after concluding that the prosecutors had failed to prove he intended to travel overseas to wage violentjihad.

U.S. officials, drawing a parallel with the Simpson case, said they were concerned that Khan might one day decide to kill someone too.

"We don't know what he is going to do in three years," the senior law enforcement official said. "We'll let the courts sort it out."

"It is almost like playing Russian roulette," said Andrew Arena, the former special agent in charge of the Detroit Field Office, which had a robust counterterrorism operation and a large Muslim population. "If you guess wrong, you got problems."

But Arena cautioned: "You're not going to arrest your way out of this problem."

At a detention hearing for Khan in Houston, federal prosecutors opposed bail.

"There are no conditions the government foresees that would enable the safety of the Homeland," Assistant U.S. Attorney Carolyn Ferko said.

A magistrate judge disagreed, placed Khan under house arrest and ordered him to wear an ankle bracelet so that his movements could be monitored.

Prosecutors appealed and told U.S. District Court Judge Lynn Hughes that Khan wanted to die fighting in Syria. They also noted that he had recruited Garcia to fight with the Islamic State.

"A man devoted to become a martyr would not turn around," said Hughes, who upheld the magistrate's decision.

The U.S. Court of Appeals for the 5th Circuit, hearing a further appeal from the government, affirmed Hughes' decision. Khan's trial is set for later this year.

Khan's father said he had read the charges against his son, but still didn't understand what he did wrong. His son turned around, he said, and did the right thing.

"He doesn't want to go to Syria," the father said. "That's what he told us. This is unfair. He did not do anything."