Two people were killed in a possible murder-suicide at an elementary school in San Bernardino, Calif., police said.

"We believe this to be a murder suicide," Police Chief Jarrod Burguan tweeted. "Happened in a class room. Two students have been transported to the hospital."

Burguan later said that two adults were deceased and two people, possibly students, were wounded and taken to a hospital. Burguan said the shooting took place at North Park Elementary School and that students were later moved to Cajon High School "for safety."

"Police operations are continuing to secure the area. However, we do believe the threat is down," Burguan tweeted.

The San Bernardino City Unified School District said the threat had been "neutralized" and that parents could pick up their kids at the high school.

Schools spokeswoman Maria Garcia described the shooting as a domestic dispute. At least two students have been airlifted to a hospital, she told the Associated Press.

San Bernardino was the site of one of the nation's worst terror attacks in December 2015. Fourteen people were killed and more than 20 wounded when a married couple stormed into a seminar and Christmas party for county workers. The shooters were later killed in a shootout with police.