SAN BERNARDINO, Calif. - 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,” Police Chief Jarrod Burguan said on Twitter. 

“Two adults are deceased in a classroom, believed to be a murder suicide,” Burguan tweeted. “We believe the suspect is down and there’s no further threat.”

Two students were airlifted to a hospital after what was believed to be a domestic dispute, San Bernardino City Unified School District spokeswoman Maria Garcia told news station KNBC-TV. The two wounded students are in critical condition. 

“We believe the teacher knew who the shooter was,” Garcia said, adding that all other students were safe.

Police did not identify the shooter or the teacher.

A San Bernardino police official said the two injured children were not the targets.

“The children we do not believe were targeted,” Police Capt. Ron Maass said. “The suspect had come to the classroom to visit. The adult female was in the classroom.” 

The school was placed on lockdown, CBS Los Angeles reported. It has about 600 students in kindergarten through sixth grades.  

Students were being taken to a local college campus, Garcia said. Students gathered on a field and a blacktop basketball court inside the fenced-in grounds of the campus near a line of school buses. 

Police told parents to go to a nearby high school to pick up their kids.

“Parents bring ID to be reunited with children at Cajon High School,” the San Bernardino Police Department tweeted. “Please be patient as it may be about 3 hours before students released.”

A robocall was sent out to alert parents about the incident, CBS Los Angeles reported. Others learned about the shooting through word-of-mouth.

Frantic parents ran up a sidewalk looking for information about their children. 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. 

Marina Ramos told news station KABC-TV that she rushed to the school to try to pick up her grandson after she heard about the shooting. She said she spoke to him, and he told her he was safe but was upset. 

“He was crying. He’s scared,” she said. “It was a typical morning and then chaos broke out.” 

Burguan said there was a “large police response.” The motive for the incident is under investigation.

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.