The killing in Ferguson was one of many such cases. Here's what the data reveals.
But quantifying that pattern is difficult. Federal databases that track police use of force or arrest-related deaths paint only a partial picture. Police department data is scattered and fragmented. No agency appears to track the number of police shootings or killings of unarmed victims in a systematic, comprehensive way.
Here's some of what we do know:
Between 2003 and 2009, the DOJ reported that 4,813 people died while in the process of arrest or in the custody of law enforcement. These include people who died before an officer physically placed him or her under custody or arrest. This data, known as arrest-related deaths, doesn't reveal a significant discrepancy between whites, blacks, or hispanics. It also doesn't specify how many victims were unarmed. According to the FBI, which has tracked justifiable homicides up to 2012, 410 felons died at the hands of a law enforcement officer in the line of duty.*