OAKLAND — Newly obtained police documents paint a clearer picture of the suicides of Oakland police officer Brendan O’Brien and his wife, Irma Huerta Lopez, including the fact O’Brien told police their argument preceding her death was over her suspicions of his infidelity with a mystery individual.

O’Brien’s suicide in September, and the note he left behind, offered the first hints of a scandal involving Oakland police officers accused of having sex with an exploited teen who goes by the name Celeste Guap.

The allegations have grown to include about 30 officers from multiple Bay Area departments, some who provided Guap with confidential information, and at least four she claims had sex with her when she was underage, which would be a crime. O’Brien is one of the four, Guap has said.

Additional details are contained in crime and forensic technician reports, dispatch records, property release and seizure reports and gunshot residue summaries provided to Bay Area News Group as part of a public records request.

They tell a story of a struggling marriage and later a depressed policeman who took his own life a year after his wife. The results of an internal affairs investigation into O’Brien’s suicide and the claims in his note — he named at least three other officers — forced the federal judge who oversees the department to place his monitor in charge of the probe in March. Since then, the department has been through three police chiefs and multiple officers have resigned and been placed on leave. Investigations into the allegations continue to this day.

Huerta Lopez’s death

Oakland police briefly investigated Huerta Lopez’s death as suspicious. Despite her family’s doubts, the Alameda County District Attorney’s Office last month confirmed the police department’s ruling of suicide in an investigation requested by Oakland Mayor Libby Schaaf. The newly released documents reveal more details of what happened on June 16, 2014. That night, officers responded to a call for an off-duty officer’s girlfriend who shot herself, according to dispatch records. Throughout the report, officers say O’Brien referred to her as his “girlfriend” rather than his wife.

The first officers arrived to the apartment on Greenridge Drive and recognized O’Brien standing in his apartment doorway, wearing a gray T-shirt, gray basketball shorts and no shoes or socks. No physical injuries were seen that would be consistent with a struggle, Officer Brandon Perry wrote in his report:

“(O’Brien) appeared to be in shock, I observed that (O’Brien) was calm, his arms and chest were shaking, he spoke in a quiet monotone voice, and he had a distant stare in his eyes,” Perry wrote.

O’Brien told officers that he went to get cigarettes from the gas station after the pair argued and that when he returned he found his wife dead with a gunshot wound to the head.

“(O’Brien) said that he and (Huerta Lopez) were in a verbal argument because (Huerta Lopez) believed that (O’Brien) was having a sexual relationship with (redacted),” Perry wrote, adding later that O’Brien told him “she believed he has been cheating on her.”

The person whose name is blacked out in the report is unknown. Guap previously told Bay Area News Group she did not start a relationship with O’Brien until after his wife’s death, in February 2015. She turned 18 in August, a month before O’Brien’s suicide.

Perry found Huerta Lopez’s body in the bedroom and noted there did not appear to be a struggle. He reported finding a “female’s wedding ring,” on a white napkin on the coffee table in the living room. Another plain band ring was found on the bedroom dresser.

A forensic technician noted “there were several neat piles of papers on the top of the table including a marriage certificate, and envelope marked “Do Not Open,” and her car registration. An officer found a large amount of clothing in the trunk of Huerta Lopez’s car.

Another officer interviewed a neighbor who had seen O’Brien in the doorway while he was waiting for police to arrive. The neighbor asked O’Brien how he was doing and he replied “not good … my girlfriend shot herself.” He told the neighbor she had used his gun, he was impatient about police not arriving yet, and he appeared to be “in shock and distraught,” according to the reports.

Another neighbor told officers the couple had been married “about two months,” but had not heard them argue in the past.

O’Brien told them it was not his department-issued gun.

Gunshot residue

Forensic pathologist William Cox reviewed the coroner’s report, crime reports, gunshot residue results and other documents involved in the case at the request of Bay Area News Group. Both O’Brien and Huerta Lopez had gunshot residue detected on their hands, which is possible since O’Brien handled guns frequently as an officer.

However, Cox expressed concerns that Oakland police and the crime lab it used did not conduct complete tests.

A one-page gunshot residue report from the Santa Clara County Crime Laboratory indicated swabs had been taken from both hands of O’Brien and Huerta Lopez and analyzed using proper equipment, Cox said.

The lab sent a summary to Oakland police: “Particles containing lead, antimony, and barium were detected on the hand samples from Brendan O’Brien and Irma Huerta and are considered characteristic of gunshot residue.”

The lab continues to say such residue could mean the subject(s) may have shot or been in proximity of a gun, handled a gun, or been in contact with a surface bearing gunshot residue.

“As done, the (gunshot residue) analysis by the Lab makes no contribution toward whether Lopez shot herself or was shot by O’Brien. It has no evidentiary value,” Cox said.

Although Cox said that “the blood splatter distribution on Lopez’s hands suggests she shot herself,” he said swabs should have been made on four surfaces of each hand, showing the distribution of the three chemicals present in gunshot residue. A particle count on each surface would provide a clear answer as to who did the shooting.

“What would have completely resolved this case, and underscored the Forensic Pathologist’s findings, was a properly done GSR analysis,” he said.

It’s not known if more testing was done. Oakland police did not respond to requests for comment.

O’Brien’s suicide

The short four-page crime report from O’Brien’s Sept. 25, 2015 suicide provided scant new information.

The suicide note which sparked the scandal was found sitting on the edge of a coffee table near his body, a semi-automatic pistol in his right hand.

Investigators found two empty Guinness beer cans in the sink and a prescription bottle of sleeping pills nearby with two remaining.

His police duty belt was seized.

Contact Matthias Gafni at 925-952-5026. Follow him at Twitter.com/mgafni. Contact David DeBolt at 510-208-6453. Follow him at Twitter.com/daviddebolt.