Once in the library, the shooter initially tried to shoot students in a "safe room," according to Seabrooks. But the students were able to barricade the door.
"He continued to shoot at them," Seabrooks said. "The officers came in and directly engaged the suspect, and he was shot and killed on the scene."
Three officers engaged the suspect according to authorities, two from the Santa Monica Police Department and one from Santa Monica College.
While authorities first stated the shootings left as many as six people dead, they later downgraded to five deaths, which included four victims and the shooter himself.
Lewis suggested the initial overcount may have been caused by overlapping witness reports of the same fatalities.
In addition to the dead, at least five people were injured, police said.
They included one critically injured person whose life was in jeopardy, a person hospitalized in serious but stable condition and three people sent to hospitals with less serious injuries, Lewis said.
The college campus went on lockdown following the shootings as police attempted to secure the scene. Students would be allowed to return for their vehicles Saturday and other belongings Sunday. The campus was expected to reopen Monday morning at 7a.m.
In 911 calls, the shooter was described as armed with several weapons.
Elsewhere on the campus, a person of interest was taken into custody, then released when his claim not to be involved checked out. According to Lewis, the man found a duffle bag belonging to the suspected shooter that had magazines, a handgun and part of a rile in side. Police temporarily detained him soon after that.
Santa Monica College student Sam Luster was preparing for a presentation in the school's library when he heard gunfire.
"We didn't know what was happening until all the students at the entrance of the library started running down towards the bottom of the library," Luster told ABC News Los Angeles station KABC.
Luster took cover under a desk before moving towards an exit. He said he heard multiple gunshots near the exit.
ABC News' Christina Ng, Michael James, Jack Date and The Associated Press contributed to this report.