Steve Marcus/Las Vegas Sun

Law enforcement officials confer during a shooting investigation in Boulder City, Jan. 21, 2013.

Las Vegas police were searching for answers Tuesday after one of their own killed his wife and son, called 911 to confess, then set his house on fire and committed suicide as rifle-toting cops moved in.

"I can't think of a reason for this, where something can get so bad that you'd do this," one veteran supervisor told the Las Vegas Review-Journal after the Monday murder-suicide.

Authorities identified the shooter as Hans Walters, 52, a lieutenant with more than 20 years on the force. His wife, Kathryn, 46, was a retired officer. Their son, Maximilian, was 5 years old.

All were shot in the head.

The family lived in Boulder City, a small community 20 miles from Sin City that boasts a low crime rate.

At 8:20 a.m. Monday, the lieutenant called 911 and said he had killed his wife and child, was setting his house ablaze and would shoot anyone who approached, a police spokesman said.

When police arrived, they found Walters in the doorway of the ranch-style home, holding a pistol.

"Put your gun down!" an officer shouted, according to a neighbor.

Walters retreated into the burning home, where he apparently killed himself, police said. The responding officers never fired a shot but circled the house with guns drawn while firefighters put out the flames that engulfed the roof.

Neighbors said the family kept to themselves. There were no details on the lieutenant's work record.

A colleague told the Review-Journal he had seen him Saturday night and he seemed "totally fine."

"You just wonder how and why this could happen," the officer said.