(KRON) — A Sonoma County Sheriff’s Office deputy who allegedly killed his former romantic partner died of a self-inflicted gunshot following a standoff with law enforcement Sunday. Deputy Jeremy Lyle was off duty when he fatally shot his former partner, Detention Specialist Mari Bonnici, according to the SCSO.

The Santa Rosa Police Department said that officers were dispatched at 7:02 p.m. to an apartment located in the 4600 block of Quigg Drive. Arriving officers were informed by dispatch that the male partner of a woman living at the apartments had handed the reporting party an infant and told her to call 911 because the child’s mother was hurt.

The man was later identified as Deputy Lyle.

Lyle, 44, who was hired in 2015, had been serving as a resident deputy in Timber Cove since 2019. After allegedly shooting Bonnici, Lyle left the scene in an unknown vehicle and headed in an unknown direction. Officers at the scene found an unresponsive woman, later identified as Bonnici. Bonnici, 38, was deceased and appeared to have sustained at least one gunshot wound.

Twin toddlers were also located in a back bedroom. All three children are believed to belong to Lyle and Bonnici. None of the children were injured and all are being cared for by family members.

Officers received word that Lyle’s vehicle was spotted parked in the parking lot of the Sonoma County Coroner’s Office. Officers responded and blocked off the parking lot.

Responding officers spotted Lyle standing in the bed of his truck holding a handgun behind his back. Initially, officers attempted to negotiate a peaceful surrender. Santa Rosa PD SWAT team members responded and took over negotiations at 9 p.m. Negotiations continued until 2 a.m. when Lyle died of a self-inflicted gunshot wound, witnessed by deputies and Santa Rosa Police Department officers.

“This tragic event is particularly shocking because it involves a law enforcement officer,” said SCSO in a social media post. “We recognize the profound shock and concern that this incident brings to our community. Both the Sheriff’s Office and the community place immense trust in those who are dedicated to serving and protecting. No level of training can fully prepare us for such a tragedy.”

“We extend our deepest condolences to Mari’s family and loved ones,” the post continued. “We are grieving alongside them and are working to support our Sheriff’s Office family.”

The incident is being investigated by the Santa Rosa Police Department.