A father fatally shot three of his children and their mother Saturday morning before turning the gun on himself at a San Diego home, police said. A fourth child remained in critical condition.

The mother, who authorities say was in the middle of a divorce with the shooter, had sought a restraining order a day earlier, San Diego Police Lt. Matt Dobbs said at a news conference.

The fourth child was undergoing surgery, police said Saturday afternoon, hours after the violence unfolded inside a “granny flat” in San Diego’s Paradise Hills neighborhood.

Police Chief David Nisleit told reporters that the apparent murder-suicide is part of a devastating larger problem.

“We know throughout this county, throughout this city, that there’s domestic violence victims every single day,” Nisleit said.

The father, 31, was pronounced dead on the scene, along with the 29-year-old mother and a 3-year-old boy, Dobbs said. Three children with gunshot wounds, aged 5, 9 and 11, were taken to the hospital, where two of them died.

Authorities have not identified any of the family members.

At 6:49 a.m. Saturday, dispatch received a 911 call in which arguing could be heard and someone was being asked to leave, according to police. But dispatchers were unable to identify or speak to the caller.

As officers headed to the scene, they got another emergency call from a relative who lived in the home near the granny flat. The relative said they had heard arguing, as well as what sounded like the firing of a nail gun, according to Dobbs.

Peering in a window, officers saw a small child covered in blood, Dobbs said. They forced their way inside to discover five more people who had been shot.

Authorities say they recovered a gun from the scene.

The violence shook responding officers, many of whom have newborn babies, Nisleit said. “If they need time off, then obviously they will be given that time off to deal with this,” he said.

Saturday was not the first time authorities responded to the home. On Nov. 1, officers arrived to “preserve the peace” after a “disturbance over property,” Dobbs said. The mother was given information on obtaining a restraining order, he said; it’s not clear if the order had been served by Saturday.

Police say the shooter was not living at the home and apparently came over Saturday morning before getting in a dispute. They plan to interview more family members for further information.