(CBS/AP) LOS ANGELES - A farewell note left behind by Santa Monica gunman John Zawahri expressed remorse for the killing of his father and brother, but provided no explanation for the deadly shooting, police say.
Police said Zawahri's 15-minute midday rampage Friday spanned a mile between his father's home, where his father and brother were shot to death, and Santa Monica College, where police shot him to death in the library. Along the way he fired at vehicles and strangers, fatally wounding three people. One other person was seriously wounded and two others had minor injuries.
Police Chief Jacqueline Seabrooks said that the three- to four-page handwritten note was found on John Zawahri's body after he was shot and killed June 7 by officers on the campus of Santa Monica College.
The 23-year-old Zawahri also used the note to say goodbye to friends and expressed hope that his mother would be taken care of and receive recompense from his father's estate, police said.
Investigators believe mental illness played a role in the killings, Seabrooks said at a news conference Thursday.
Zawahri apparently built his own .223-caliber assault rifle, using it to shoot his father and brother before he set fire to their family home, according to officials.
Seabrooks said the semi-automatic weapon appears to have been built with component parts that are legal to obtain, but put together make the rifle illegal in California.
Zawahri carjacked a woman, directing her to the college and having her stop so he could fire at vehicles and strangers, police said. Police say they still did not know why he chose to go to the college, why he targeted those killed or why he chose that day.
Though Zawahri fired about 100 rounds during the rampage, police said he was carrying 1,300 rounds of ammunition in magazines that were capable of holding 30 rounds each. Such high-capacity magazines are illegal to purchase, sell or transfer in California. Possession is not illegal. He also had a spare upper receiver and the antique revolver with him in a duffel bag.
The rampage ended when police shot and killed him at the college's library.