Fentanyl is an opioid -- similar to heroin -- used to treat the worst pain cancer patients experience. The drug is so powerful, doctors prescribe it in micrograms. It's incredibly addictive and deeply dangerous. From 2005 to 2007, more than 1,000 deaths were blamed on the drug.

Twenty-eight-year-old surgical technician Rocky Allen has allegedly been stealing it from hospitals for years.

In January, Allen was indicted on charges of tampering with a consumer product and obtaining a controlled substance by deceit for allegedly stealing this drug from Swedish Medical Center in Englewood, Colo., a suburb of Denver. He worked there from last August to January 2016, according to KDVR.

Further investigation found he'd been allegedly stealing the liquid drug and the syringes containing it for years, job-hopping from hospital to hospital across four states in the American West. In fact, he was court-martialed and discharged from the Navy for stealing fentanyl from a hospital in Kandahar, Afghanistan, where he was posted in 2011.

His method of thievery allegedly involved switching out fentanyl-filled syringes with ones he would sneak into the hospital that contained a saline solution, the Los Angeles Times reported.

On Wednesday, federal officials announced Allen is HIV-positive, the Denver Post reported. Since there's no way of knowing if he ever used the syringes he switched the originals for, thousands of former patients could be at risk for the disease.

According to a statement from Dr. Larry Wolk, chief medical officers and executive director of CDPHE, Swedish hospital has tried to notify about 3,000 patients who may be at risk. Thus far, no one appears to be infected, but the Colorado Department of Public Health and Environment said 1,000 people in Colorado alone still need to undergo testing, KDVR reported.

"At this point we have no evidence of any patient exposure," Swedish Medical Center said in a statement reported by the Denver Post when Allen was first accused of theft. "However, we are taking a position of extreme caution by offering free testing to all patients who had surgery at Swedish Medical Center in locations where this individual worked at any time during this individual's employment, including those days the employee was not on the schedule or in the facility."

Authorities said that this same situation "occurred at virtually each and every healthcare facility" Allen has worked for since 2011, according to the Los Angeles Times.

The tech claimed to become addicted to the drug while in the Navy as a means of "escape" from the bloodshed he witnessed in the Kandahar military hospital where he worked. He admitted to stealing 30 syringes of fentanyl from a drug locker there, which he claimed to have thrown out of the trash in a nervous panic.

"I have learned so much from this experience," Allen said in 2011. "I know that it has made me stronger."

But less than three months after being discharged, he was fired from his new job at Lakewood Surgery Center in Lakewood, Wash., on suspicion of drug theft.

Thus began his long string of jobs that generally ended in termination: Fired after two months at Northwest Hospital in Seattle for "alleged misconduct," from Scripps Green Hospital in La Jolla for hiding a syringe of fentanyl in his sock, from Banner Thunderbird Medical Center in Glendale, Ariz. on suspicions of drug theft, from HonorHealth John C. Lincoln Medical Center in Phoenix after allegedly being found unconscious in the bathroom with an empty syringe and testing positive for fentanyl.

In response to Allen's history of alleged syringe-swapping coming to light, Denver-based lawyer James Avery has filed lawsuits against Swedish Medical Center, Banner Thunderbird Medical Center and HonorHealth John C. Lincoln Medical Center on behalf of former patients, the Denver Post reported.

All of the aforementioned hospitals have asked former patients to get tested for blood-borne diseases, the Los Angeles Times reported. In total, some 6,350 are potentially at-risk.

This isn't the first time a medical technician has put others at risk to support his or her own addiction.

In 2013, David Kwiatkowski was sentenced to 39 years in prison for stealing syringes of fentanyl, using them and then putting the same syringes back at New Hampshire's Exeter Hospital while knowingly having been diagnosed with hepatitis C, CNN reported. A multi-state outbreak of the disease occurred as a result. Three years before that, a surgical tech who worked in Denver and Colorado Springs was sentenced to 30 years for doing the same and infecting at least 18 patients with hepatitis C, the Denver Post reported.

Some said techs are able to conceal their addictions -- and employment histories -- due to a lack of a central tracking system for hospital technicians with access to drugs. According to the Associated Press, current Colorado law only required Allen to self-disclose his civil, criminal or administrative record, which Allen easily side-stepped by allegedly leaving some of his past hospitals of employment off his resume.

Swedish Medical Center claimed to have done further background checks. Hospital spokeswoman Nicole Williams told the Denver Post, "Like most hospitals, our hiring process includes a background check by a third party, interviews by managers and peers, confirmation of training and certification, state registration and pre-employment drug screening."

Still, according to the Julianne D'Angelo Fellmeth, administrative director of the Center for Public Interest Law at the University of San Diego's law school, the background check requirements for hiring hospital technicians are often riddled with holes, even though many of these employees have access to narcotics and medical tools, the AP reported.

Diana Protopapa, a lobbyist for surgical technicians in Colorado, agreed.

"[This] means the lack of regulation of surgical technologists and assistants nationwide poses a serious threat to patient safety," she told the Denver Post. "This is ridiculous."

Allen is currently out of jail on a $25,000 bond and is set to stand trial in August.