A special education teacher and an eight year old student were killed by her estranged husband who opened fire in a classroom of 15 children with special needs before killing himself on Monday in San Bernardino, California. Another student, 9, was injured in the incident. The local police described it as a “murder-suicide” attempt, reported BBC.

The shooter has been identified as one Cedric Anderson, 53. He is believed to have entered the school as a visitor on Monday morning. Investigators said Anderson was married to the victim, Karen Elaine Smith, for a short period of time, and they had separated around a month ago, reported Reuters. Reports suggested that the incident was triggered by domestic dispute, however, the police have yet to confirm the reason behind the shooting.

There were at least 600 children in the North Park elementary school when the incident took place. “Police operations are continuing to secure the area,” local police chief Jarrod Burguan said on Twitter. “However, we do believe the threat is down.”

A couple had killed 14 health workers in December 2015 when they opened fire in a disabled service centre in San Bernardino. At least 21 people were injured in the incident.