This past week, a Milwaukee toddler fatally shot his mother after finding a handgun in the back seat of the car they were riding in. The case drew a lot of national attention given the unusual circumstances: Little kids rarely kill people, intentionally or not.

But this type of thing happens more often than you might think. Since April 20, there have been at least seven instances in which a 1- , 2- or 3-year-old shot themselves or somebody else in the United States:

On April 20, a 2-year-old boy in Indiana found the gun his mother left in her purse on the kitchen counter and fatally shot himself.

The next day in Kansas City, Mo., a 1-year-old girl evidently shot and killed herself with her father's gun while he was sleeping.

On April 22, a 3-year-old in Natchitoches, La., fatally shot himself after getting hold of a gun.

On April 26, a 3-year-old boy in Dallas, Ga., fatally shot himself in the chest with a gun he found at home.

On April 27, the Milwaukee toddler fatally shot his mother in the car.

That same day, a 3-year-old boy in Grout Township, Mich., shot himself in the arm with a gun he found at home. He is expected to survive.

On April 29, a 3-year-old girl shot herself in the arm after grabbing a gun in a parked car in Augusta, Ga. She is also expected to survive.

Last year, a Washington Post analysis found that toddlers were finding guns and shooting people at a rate of about one a week. This year, that pace has accelerated. There have been at least 23 toddler-involved shootings since Jan. 1, compared with 18 over the same period last year.

In the vast majority of cases, the children accidentally shoot themselves. That's happened 18 times this year, and in nine of those cases the children died of their wounds.

Toddlers have shot other people five times this year. Two of those cases were fatal: this week's incident in Milwaukee, and that of a 3-year-old Alabama boy who fatally shot his 9-year-old brother in February.

These numbers represent only a small fraction of gun violence involving children. For instance, the pro-gun-control group Everytown for Gun Safety has found at least 77 instances this year in which a child younger than 18 has accidentally shot someone. And there is a whole different universe of gun violence in which toddlers are shot, intentionally or not, by adults.

Looking at where toddlers are pulling the trigger, some states stand out sharply.

Georgia is home to the highest number of toddler shootings, with at least eight incidents since January 2015. Texas and Missouri are tied for second place with seven shootings each, while Florida and Michigan are tied for fourth, with six shootings apiece.

You might think that toddler shootings are simply a function of population - the more people who live in an area, the more toddlers are likely to shoot someone. But that doesn't appear to be wholly the case. California and New York are two high-population states that have seen only three toddler shootings between them since 2015.

And Illinois, home to infamously high rates of gun violence in Chicago, has not seen a single toddler shooting since 2015.

This suggests that other factors may be at play in the states that see disproportionately high numbers of shootings by toddlers. Missouri and Georgia, for instance, have fairly lax laws regulating how guns are stored to prevent child access. On the other hand, New York has no such child access laws in place, yet only one toddler has shot someone there since 2015.

Perhaps other factors are at play as well. There could be cultural factors - norms surrounding gun use and ownership, for instance - that may make these shootings more likely in some areas than in others.

Sussing out cause and effect in these cases, in other words, is still largely a guessing game. And it's a game made much more difficult by Congress' efforts to restrict the type of gun research that agencies such as the Centers for Disease Control and Prevention are allowed to conduct.

Until 2004, for instance, the CDC routinely asked Americans about whether they stored guns at home, and whether they made a habit of locking them up. That's no longer the case.