Five members of a San Diego family died in a domestic violence murder-suicide incident on Saturday morning, Nov. 16, after a father shot his wife and his sons before turning the gun on himself. Three of the four sons died and the 9-year-old son remained in critical condition, the Washington Post reported.

Police were dispatched to the home in Paradise Hills after getting a 911 call where no one spoke, but an argument could be heard in the background. While police were on their way to the home, another 911 call came in from a relative living nearby who heard arguing and what sounded like the firing of a nail gun, San Diego Police Lt. Matt Dobbs said.

When authorities arrived at the home, police found the 31-year-old father, 29-year-old mother, and four sons, ages 3, 5, 9, and 11 all with gunshot wounds. The parents and their 3-year-old were pronounced dead at the scene, and two of the other children died at the hospital, according to NBC San Diego. The fourth child 9, who underwent surgery, was in critical condition.

“It’s still very early in the investigation but it appears to be a tragic case of domestic violence, murder-suicide,” Dobbs said. “We believe the male came over this morning, there was some kind of argument or disagreement and he used a handgun and shot his family before turning the gun upon himself.”

The mother, who was in the middle of a divorce with her husband, had filed a restraining order against him a day before the shooting, authorities said.

Her sister claimed the husband refused to go through with the divorce and had been stalking his wife after they separated.

They had responded to a “disturbance over property” at the home on Nov. 1, when the husband—who was not living at the home—showed up asking her for tools. Officers who responded to the call informed the woman about how to obtain a restraining order, The New York Times reported.

San Diego Mayor Kevin Faulconer called the tragedy “terribly sad.”

“All of San Diego mourns for the family and the surrounding neighborhood,” he tweeted. “This senseless act of violence goes against everything our community stands for and we will get through this together.”