The gunman who killed at least four people in a shooting rampage at Santa Monica College yesterday had previously been hospitalized and treated for talking about wanting to harm someone.

CNN is reporting that the unidentified shooter was treated for mental health issues "a couple of years ago" but sources aren't sure whether he hospitalized himself or whether he was involuntarily committed.

The FBI has joined local police in investigating the gunman to determine his motives. Investigators believe he first shot and killed his father and brother, then set the house on fire. Dressed in all-black with an AR-15 style rifle and a handgun, authorities believe he then carjacked a woman and demanded she that she drive him to Santa Monica College. As they drove, the gunman shot at a public bus and a Ford Explorer, injuring and killing multiple victims.

The gunman got out of the car and let the woman go once they reached the school. He ran through the school to the library, shooting at people as he went. He was shot and killed by police officers, and died on a sidewalk.

[CNN, photo via AP]