Fatal Encounters is a project that explored the tensions of police shootings and killings. The nation's approximately 18,000 police agencies are expected to submit specified categories of crime statistics every year to the FBI's Uniform Crime Reporting program. There is no national database. This data is combined from a few sources.
"No one anywhere comprehensively tracks the most significant act police can do in the line of duty: take a life,” according to the Las Vegas Review-Journal in its series Deadly Force (Nov. 28, 2011).
See it here: http://fatal.ctodd.co/