Most of the people police kill are armed

Police killings of unarmed people can generate enormous public outcry and a lot of media attention. Think of Stephon Clark in Sacramento, Oscar Grant in Oakland and Michael Brown in Ferguson, Mo. But the data show that the majority of people police kill are armed with a gun or a knife. Many others are holding a toy gun.

Experts disagree whether police should shoot a suspect holding a knife. Though knives are deadly weapons that can legally justify using lethal force, Franklin Zimring, a professor at the UC Berkeley law school, argues that police should generally be prohibited from firing at suspects wielding blades. 

His book, When Police Kill, is an exhaustive look at the violence in both directions. Zimring studied six years of data on intentional killings of police and found that more than 97% of them were by gunshots. Only two officers died from knife injuries, leading Zimring to argue that police may unnecessarily kill hundreds of Americans each year who are holding knives.