Two adults were shot and killed at a California elementary school Monday in what police believe to be a murder-suicide and two students were rushed to a hospital with unknown injuries.

The incident happened around 10 a.m. local time at the North Park Elementary school in San Bernardino.

“Two adults are deceased in a classroom, believed to be a murder suicide,” San Bernardino Police Chief Jarrod Burguan posted on Twitter. “We believe the suspect is down and there’s no further threat.”

Burguan added that two students have been transported to a hospital. Their conditions are unknown.

One of the victims is believed to be a teacher and responders are on scene, Maria Garcia, communications officer at San Bernardino Unified School District, told Fox News. 

The school is on lockdown along with two others: Hillside Elementary School and Cajon High School.

Garcia told the San Bernardino Sun that school officials believe the “situation is contained.”

All other students were safe and were being taken to Cajon High School, where parents or guardians could pick them up, she 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.

The school has about 600 students in kindergarten through sixth grades.

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.”

Federal law enforcement sources told Fox News that the San Bernardino Police Department is the lead agency responding to and investigating the shooting. The ATF’s Los Angeles division has also lent assets to San Bernardino police and the FBI has offered its assistance, the sources added.

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.

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Fox News’ Matt Dean and the Associated Press contributed to this report.contributed to this report.