"I don't know." That's the response the North Miami police officer gave to shooting victim Charles Kinsey, when he asked why the officer opened fire as he lay flat on the ground, hands outstretched to prove he was no threat to the police.

On Sunday, police identified Gavin Long as the shooter who killed three officers in an eight minute standoff. Details emerge about the 29-year-old ex-Marine and what motivated him to take what he called justice into his own hands.