EAST COUNTY — Employees of the Barona Gaming Commission got together for counseling and then went to work as a group yesterday, the first time they returned to their offices since a former investigator killed a manager and then himself a week ago.

“It was pretty somber,” said Kathryn Clenney, a member of the gaming commission and the tribe’s top lawyer.

Nobody had an explanation for why former investigator Donnell Roberts returned to the commission’s offices with a shotgun Tuesday, a month after he resigned following an investigation, killed Executive Director Ray Casillas and committed suicide.

A sheriff’s spokeswoman said she had no public update on the homicide investigation.

The biggest change came in the form of additional security, Clenney said. But without an explanation for what happened, there’s not much more to do.

“I don’t know how you can prevent it, unless you’re giving psychological tests to everybody,” she said. “It’s not something I saw coming. I don’t think anybody did.”

The commission’s workers, like those at the casino it regulates, are subjected to extensive background checks that are updated every two years.

A felony, or a crime of dishonesty, can disqualify someone from getting or keeping a gaming license.

“We do it on everybody,” Clenney said. “Really, for the integrity of the casino.”

The gaming commission is the primary regulator for the Barona Resort & Casino.

Workers investigate allegations of cheating — by gamblers as well as the casino — and conduct background checks. They enforce food and water standards. They let the casino’s managers know whether proposed games or machines pass muster.

“There’s regulation about pretty much everything, from the way they pull money out to how they access the machines, what they do with cards,” Clenney said.

Key casino and gaming commission employees, those with upper-management responsibilities, not only must get the approval of the tribal gaming commission, but also from state regulators.

Roberts was not licensed by the California Gambling Control Commission, but he was not upper-management.

George Forman, a lawyer who has long worked with tribes in California, said the tribal commissions have higher standards than Nevada.

“You can get a job in a Las Vegas casino with a felony conviction,” Forman said. “You cannot get a job in a California tribal casino with one.”

Gaming commissions are set up by each tribe and they operate under the rules of the tribal government, Forman said. Like a state regulator that oversees lottery operations, the commissions have the power to step in if there’s a problem.

“They’re professionally staffed,” Forman said. “They operate independently of the tribal council, typically. … It’s in the tribe’s interest to have an effective regulator.”

Tribal gambling watchdog Cheryl Schmit, who heads a coalition called Stand Up for California, said the quality of the regulation depends in large part on who works there and how independent they are from the tribal power structure.

“That’s left up to each tribe,” Schmit said.

Some California tribes have well-respected commissioners who set strong policies, she said. Others are not as good.

“They are paid for by the tribe, and they answer to the tribe,” Schmit said.

Some former commissioners have told her they were fired after exposing skimming by tribal members. Schmit said she was not speaking about Barona.

Larger, more sophisticated operations tend to have better regulation, she said.

That’s in part because they have the resources to draw people from around the country, said Alison Harvey, who chairs the gaming commission for Northern California’s Litton Indian band.

“They can bring in people from other states that have a lot of experience,” Harvey said.