The graduation got under way at 6 p.m. on the football field. Students were still shaken up by the shooting spree that ended at their campus.
Some graduating students said they weren't planning to take part in the ceremony.
"I wasn't going to walk because I didn't want to celebrate," said graduate Claudette Colbert.
Colbert said school counselors convinced her to attend her graduation celebration.
"I'm very glad I did. I was actually thanking the counselor because it made you realize that things will happen. You must continue. You can't let anything stop you," said Colbert.
Police say suspected gunman, 23-year-old John Zawahri, killed his father Samir and his brother Chris before going on his rampage, killing Carlos Navarro Franco, 68, his daughter Marcela Franco, 26, and Margarita Gomez, 68, of Santa Monica, who was collecting cans and bottles for members of her church.
The Santa Monica College library remains a crime scene and will not reopen until June 18.
Meantime, more details continue to emerge about the suspect. Police found bomb-making materials seven years ago in his home. According to a member of the Santa Monica Malibu Unified School District, police discovered the materials after Zawahri threatened fellow high school students in 2006 while he attended Olympic High School.
Court records also allege years of turmoil in the Zawahri family. The gunman's father reportedly threatened to kill his wife and was verbally abusive and controlling.