Authorities say the former investigator for the Indian tribal casino's gaming commission shot and killed a man in the office before fatally turning the gun on himself Tuesday.
"Our worst fears were confirmed," San Diego County Sheriff Bill Gore told reporters outside the convention center of the Barona Resort and Casino. "It appears to be a murder-suicide."
Roberts, 38, ordered three secretaries to leave when he entered the Barona Gaming Commission building around 10 a.m., and another 13 to 15 employees fled through a back door, Gore said. Witnesses heard three shots fired.
Within about an hour, authorities accounted for everyone who was inside the building except one, Gore said. He declined to identify the victim until his family was notified.
Roberts, of El Cajon, Calif., was fired in November as an investigator with the commission and worked previously as a security guard for the casino.
San Diego County sheriff's deputies and California Highway Patrol officers surrounded the gaming commission building, located behind the casino. The wait ended after two robots captured images of the bodies.
Authorities never established contact with Roberts, Gore said.
The casino in the east San Diego suburb remained open throughout the ordeal but a parking garage and day-care center were closed, said Rick Salinas, the casino's general manager.
Salinas said he didn't know why Roberts was fired from the commission, which functions as the tribe's regulator of its casino. He was one of about three investigators and 30 to 40 employees working for the commission.
"He was a professional, he did his job, and from my understanding he did it well," Salinas said.
Gore said the employees he spoke with were "very distraught."
"It's been a very traumatic day for all of them, I'm sure," he said.
The resort, which includes a 400-room hotel, golf course and spa, is operated by the Barona Band of Mission Indians and employs about 3,000 people.
The tribe bought the reservation property in 1932 after its original reservation land was used to build a reservoir. Tribal gaming began there in 1994 with the opening of the Barona Casino Big Top.
