SAN BERNARDINO, Calif. (AP) — An apparent murder-suicide inside an elementary school classroom in San Bernardino left two adults dead, including a teacher, and two students wounded, police and school officials said.

Investigators believe "the suspect is down" and there is no further threat to North Park School, Police Chief Jarrod Burguan said on Twitter.

Two students were airlifted to a hospital after what's believed to be a domestic dispute, San Bernardino City Unified School District spokeswoman Maria Garcia told news station KNBC-TV. Their conditions were not immediately known, police said.

"We believe the teacher knew who the shooter was," she said.

She said all other students were safe and they were being taken to a local college campus. Aerial footage showed students gathered on a field and a blacktop basketball court inside the fenced-in grounds of the campus as school buses lined up.

Frantic parents ran up a sidewalk looking for information about their children but were not able to learn immediately what happened at the school. Several parents interviewed on TV said their children were too young to carry mobile phones, so they had not been able to contact them to see if they were safe.

The city of 216,000 was the site of the December 2015 terror attack that killed 14 people and wounded 22 others at a meeting of San Bernardino County employees. Husband-and-wife shooters Syed Rizwan Farook and Tashfeen Malik were killed in a gunbattle with authorities later that day.

The city is known for its high rates of violent crime, especially homicides, and has struggled to emerge from bankruptcy.