The assailant was identified as Oakland resident Lovelle Mixon, age 26, who worked sporadically as a plumber and custodian. Mixon wielded two different weapons—a semiautomatic handgun and an SKS rifle—during his deadly assaults on the Oakland police officers.
Mixon had an extensive criminal history. Beginning at age 13, he was arrested multiple times for battery, and by age 20 he began serving a Corcoran state prison sentence following a felony conviction for assault with a deadly weapon during an armed robbery in San Francisco. After he was paroled, Mixon was in and out of prison. At the time of his assault on the officers, he was living in East Oakland at his grandmother's house and was wanted on a no-bail arrest warrant for violating his current parole conditions. On March 20, 2009, the day prior to the police shootings, Oakland police learned that Mixon was linked by DNA to the February 5, 2009 rape of a 12-year-old girl who was dragged off the street at gunpoint in the East Oakland neighborhood where Mixon's sister lived. On May 4, 2009 a state laboratory confirmed this link and also said Mixon had robbed and raped two young women on the morning of March 21, 2009, the same day he murdered four police officers. Investigators said that Mixon may have committed several other rapes during recent months, although no convictions had been secured before his death. If Mixon had been arrested for his parole violation, he would have faced at most six months in prison; if convicted of rape, he faced a life sentence.
Mixon had also been the primary suspect in a previous murder case, however due to lack of evidence he had been charged only with lesser violations: possession of drug paraphernalia, forgery, identity theft, attempted grand theft, and receiving stolen property.