On December 20, 2014, a twenty-eight-year-old man named Ismaaiyl Brinsley walked up to a parked patrol car in the Bedford-Stuyvesant neighborhood of Brooklyn, pulled out a semiautomatic handgun, and fired several shots at the officers sitting inside, Wenjian Liu and Rafael Ramos, killing them both before either could draw his own gun. Brinsley then ran down into a subway station and killed himself. He had written on social media that he wanted revenge for Michael Brown and Eric Garner, two unarmed African-American men who had been killed by the police that summer. Brinsley was a troubled individual who earlier…