A teenager was killed and three people were wounded, including an 11-year-old, when gunfire erupted outside a high school graduation ceremony in Northern California, according to police.

The shooting took place at about 7:15 p.m. local time Wednesday in the parking lot of Fairfield High School after a ceremony ended there for Sem Yeto High School graduates, the Fairfield Police Department said.

Four victims were shot, police said. An 18-year-old died while an 11-year-old, a 20-year-old and a 25-year-old were injured, police said.

It’s not clear if the 18-year-old was a graduating student.

There is no ongoing threat to the community, police said, but they did not comment on the suspect or suspects involved.

About 1,000 people were at the graduation “with hundreds of potential witnesses to this tragedy,” police said in a statement on Thursday.

“Detectives are currently identifying and interviewing these witnesses and are actively following up on investigative leads,” police said.

The Fairfield-Suisun Unified School District said in a statement, “Our thoughts are with the individuals affected.”

ABC News’ Bennett Garcia contributed to this report.