Alameda County D.A. conducts parallel Oakland police inquiries

Oakland Mayor Libby Schaaf, left, speaks beside Oakland Chief of Police Sean Whent on Friday, May 13, 2016, in Oakland, Calif. An Internal investigation has been launched into alleged sexual misconduct by three Oakland police officers. (AP Photo/Ben Margot) less Oakland Mayor Libby Schaaf, left, speaks beside Oakland Chief of Police Sean Whent on Friday, May 13, 2016, in Oakland, Calif. An Internal investigation has been launched into alleged sexual misconduct by three ... more Photo: Ben Margot, Associated Press Photo: Ben Margot, Associated Press Image 1 of / 1 Caption Close Alameda County D.A. conducts parallel Oakland police inquiries 1 / 1 Back to Gallery

The Alameda County district attorney has begun an investigation into the possibility of sexual misconduct by three Oakland police officers and will look at whether the Police Department properly investigated the 2014 shooting death of another officer’s wife, Oakland Mayor Libby Schaaf said Friday.

The two issues may be related. Suspicions of sexual misconduct by the three unidentified officers — who have been placed on administrative leave — arose in September when the dead woman’s husband, Officer Brendan O’Brien, committed suicide, Police Chief Sean Whent said at a news conference Friday with the mayor. He would not confirm recent media reports that O’Brien had left a suicide note referring to the sexual misconduct or say much about what happened at all.

But news has leaked out about the allegations, and as questions have been raised about the police investigating themselves, the mayor called the news conference to announce the heightened level of oversight and to say that officers are held “to the highest standard of conduct.”

Whent defended the department’s finding that O’Brien’s wife had committed suicide more than a year before he died. On June 16, 2014, O’Brien found his wife, 29-year-old Irma Huerta Lopez, dead in their Oakland apartment with a gunshot wound to her head, according to the Alameda County coroner’s report. The report also ruled the death a suicide, noting that there was no sign that she had struggled or tried to defend herself.

A semiautomatic handgun found at the woman’s feet was reportedly O’Brien’s service pistol, which had been fired twice. A second bullet was reportedly found in the apartment wall.

The fact that the gun had been fired twice, and that the coroner found no gunpowder on Huerta Lopez’s hands, raised questions about whether she had killed herself.

But police said Friday that they did find gunshot residue on the woman’s hands and that the second bullet did not prove homicide.

“It’s not uncommon for suicides to have more than one round” fired, Whent said.

As for O’Brien, he had told police he was at a convenience store when his wife died. Police released a written statement saying they had a receipt corroborating that claim as well as surveillance video placing O’Brien at the store around the time she died.

“But I’d certainly like them to see if there’s anything we missed,” Whent said, referring to the district attorney’s investigation of the matter.

In September, O’Brien committed suicide. That’s when police began looking into sexual misconduct on the part of three officers, Whent said, but he declined to comment on details, including the message the officer reportedly left behind.

Until Friday, regulations required police to notify the district attorney’s office only after concluding an investigation into criminal activity on the part of officers, on or off duty.

That’s changed now, said Schaaf, who joined Whent at the news conference. The mayor said she has directed police to notify the district attorney at the beginning of such investigations so the district attorney can decide whether to conduct it instead, she said.

The district attorney has begun “a parallel and independent investigation” into the potential sexual misconduct and how the Huerta Lopez death was handled, Schaaf said, noting that it will also look at the Police Department’s investigative process.

Jenna Lyons and Nanette Asimov are San Francisco Chronicle staff writers. Email: jlyons@sfchronicle.com, nasimov@sfchronicle.com Twitter: @JennaJourno, @NanetteAsimov