ST. LOUIS — A man found dead inside a burned home in southern Illinois had been shot in the head, and a gun was found in his ex-wife’s SUV after she drove into a nearby lake and died shortly after the fire was reported, authorities said Friday.

The pair’s infant son was pulled from the submerged SUV by a paramedic who swam through frigid water, quickly realized a baby and not a doll was floating inside, and performed CPR on the boy atop the vehicle’s roof. Six other children safely escaped the Thursday fire at the house, where the divorced parents — who had a history of domestic violence — both lived.

Preliminary autopsy results released Friday show 37-year-old Justin Campbell died from the gunshot wound. But testing can’t be done to determine whether the gun found in Cristy Campbell’s SUV was used to shoot Campbell because the bullet that struck him hasn’t been found, according to Madison County Coroner Steve Nonn.

Nonn later told The Associated Press that nothing in the investigation or autopsy suggests the gunshot wound was self-inflected.

Police said the tangled chain of events began when some of the children ran to a Wal-Mart store near their home around 5:15 a.m. Thursday in Glen Carbon, Illinois. They told an arriving worker to call 911 because their house was on fire. Responding firefighters found Justin Campbell’s body.

About 16 minutes later, a motorist called 911 after seeing an SUV travel down a hill and into Silver Lake in Highland, about 16 miles away from the house.

Paramedics Todd Zobrist and Ty Barr arrived minutes later. Zobrist said he could see headlights in the water and knew there might be someone inside the SUV, which was submerged in about 5 feet of water. He stripped off his shirt, socks and boots, and swam 75 feet to the vehicle.

“When I got halfway there I was thoroughly thinking to myself, ‘This is a terrible decision and I really need to just turn around and go back to the dock because I’m going to get myself in a lot of trouble,’” Zobrist said at a news conference Friday. “At that point, though, I was committed, I was already wet, I was already cold.”

Dark outside and difficult to see, he found the only access inside the vehicle was through an open driver’s side window. Zobrist peered into the back seat — and saw something.

“It looked like two feet and two hands,” he said. “And at first I thought it was just a doll, a kid’s toy of some sort.”

It was 3-month-old Julian Campbell, alone and floating inside the SUV with about 8 inches of air space.

Zobrist pulled the unresponsive infant out the window and began CPR on the SUV’s roof. Once the baby spit out water and began breathing, Zobrist, his muscles aching from the cold, called back to his partner to see if firefighters with a boat and wetsuits were coming. But the team was delayed by a train, so Zobrist swam back to shore with the baby in one arm. The baby was hospitalized and expected to recover.