ISLA VISTA, Calif. (NBC News) -- Authorities say the manifesto left behind by Isla Vista gunman Elliott Rodger indicates he had been planning his deadly attack for years.
"Tomorrow is the day of retribution...the day I will have my revenge against humanity," Rodger said in one of the final videos he recorded before he killed three roommates, then opened fire on random victims near his apartment.
Earlier videos last month alarmed his family, who called mental health experts for a welfare check.
Rodger recalled in the 140-page manifesto he sent to his parents minutes before the shootings that he'd told deputies at his door it was all a misunderstanding.
"Thankfully," he wrote, "all suspicion of me was dropped."
Santa Barbara County Sheriff Bill Brown says with no indication that he was an immediate threat to himself or others, there was nothing else they could do.
-- Jennifer Bjorklund reports