The San Diego County Medical Examiner"s Office Wednesday identified the 43-year-old manager killed Tuesday at the personnel offices next to Barona Resort & Casino as Raymundo Castillas.

Castillas was shot to death with a shotgun Tuesday morning by 38-year-old Donnell Roberts of El Cajon. Roberts then took his own life.

Roberts ex-wife described the gunman as perennially unhappy and enraged over being fired.

"He told me, `I lost my job but I have something in the works,'" Maria Small, now a Wisconsin resident who was previously married to 38-year-old Donnell Roberts of El Cajon, told The San Diego Union-Tribune in a telephone interview.

"I knew that there was that rage there. I just didn"t think he would go through with it.'"

Castillas lived in La Mesa and was the commission's executive director for the past year, the Union-Tribune reported. He arrived after holding a similar post for the Salt River Pima-Maricopa Indian Community, which has two casinos in Scottsdale, Ariz., according to the newspaper, which reported that Castillas' wife and children still live in Arizona.

Roberts entered a personnel trailer at the Lakeside-area office complex with a shotgun shortly before 10 a.m., told several receptionists to leave, walked into an office and began shooting, San Diego County Sheriff Bill Gore said. Witnesses near the trailer reported hearing three shots.

"Shortly after all the employees evacuated, and we knew there were two people left in the building, the shooter and the victim, we ... set up a perimeter," Gore said. "And then we called in our SWAT teams... And once that was done ... we tried to establish communications with whoever was inside, to no avail."

About 2:30 p.m. Tuesday, deputies sent a camera-equipped remote-control device into the office complex and determined that two people were inside, apparently dead, Gore said. Sheriff"s personnel then entered the trailer and confirmed the deaths.

Roberts was a one-time Barona Casino security guard who later was given a white-collar job on the staff of the gaming commission -- until last month, when he was fired for undisclosed reasons, said sheriff's spokeswoman Jan Caldwell.

It was not immediately clear whether it was Castillas who fired Roberts, who had lived alone in an apartment in El Cajon since September.

Rick Salinas, general manager of Barona Resort & Casino, said he was not aware of any problems with Roberts.

"He was a professional," Salinas said. "He did his job and from my understanding he did it well."

Roberts' ex-wife said she last spoke with Roberts on Christmas Day.

"He was always angry," said Small, who has custody of the 12-year-old daughter she had with Roberts. "It was more of a sadness. He was never happy with anything -- never."

The couple divorced in 2006 after 13 years of marriage, the Union- Tribune reported.

Small told the newspaper that Roberts had six children with other women and that his father, a police officer in Cambridge, Md., committed suicide when Roberts was 10.

Roberts served in Operation Desert Storm and was discharged from the Marine Corps in 1994, the Union-Tribune reported.