The hand-held video of 25-year-old Kajieme Powell’s last moments has generated a lot of controversy, and appropriately so. You see Powell wandering around on a sidewalk in St. Louis—looking confused and mostly ignoring passersby, until a pair of police officers show up in a squad car. He approaches them, coming within a few feet before the officers fell him with a dozen rapid shots. According to the police, Powell was wielding a knife and acting in a threatening manner, and yelled at the officers to shoot and kill him as he approached.

Did the cops overreact? Some witnesses at the scene said it looked like a “suicide-by-cop.”—i.e., Powell was intentionally provoking an armed police officer to shoot him for certain death. And while Sam Dotson, the chief of the St. Louis Police, said he disagreed, Fox News pundit Geraldo Rivera quickly picked up the charge on his twitter feed, and implied it was because Powell was on drugs. “The new suicide-by-cop crowd (urban equivalent of suicide bombers) — young men who irrationally confront edgy cops who kill them — are on Dip.”

It’s an over-the-top statement, which is pretty standard behavior for Rivera. There's obviously no way to know what Powell was actually thinking before the police shot him. But there are some genuinely complicated and important questions lurking in all this talk about suicide-by-cop. What responsibilities do police officers have when they are confronting people who are threatening them, maybe even provoking a response, but seem mentally ill or intellectually disabled? Is anybody training them for situations like this?

There isn’t great information on just how often suicide-by-cop occurs, in part because not everybody agrees on the definition. In one 1998 article, published by the Federal Bureau of Investigation, criminal justice professors suggested that the suicide-by-cop accounted for 16 percent of all shootings by police, but that at least some suicidal motivation played a part in nearly half of all shootings. A more recent study, which police psychologist Kris Mohandie published in the Journal of Forensic Studies in 2009, found suicidal motivation accounted for 36 percent of more than 700 North American police shootings.

Whatever the ambiguities of the data, there’s no question that police officials are constantly dealing with people who have mental illness. In one 1999 study, psychiatrists found 7 percent of all police investigations and complaints involved a mentally ill person in one 1999 study. California’s police training commission puts the rate of calls involving someone with a likely mental illness at 15 percent.