A gunman entered a western Arizona home and fatally shot five people, including the mother of his two children and her new boyfriend, before fleeing with the kids to Southern California where he killed himself, police said Sunday.

The shootings late Saturday occurred as 23-year-old Deborah Langstaff and friends were celebrating her boyfriend's birthday, Lake Havasu City police Sgt. Joe Harrold said. In all, six people died.

Police went to the Lake Havasu City home after dispatchers received an emergency call at 11:57 p.m. Saturday from a woman who said an intruder had shot several people.

Officers responding to the home said they found the bodies of Langstaff, Primo Verdone — who had just turned 24 — Russell Nyland, 42, and Ashley Nyland, 20.

Two others were wounded, but 20-year-old Brock Kelson died of his injuries early Sunday. Deborah Nyland, 44, was in intensive care at a Las Vegas hospital Sunday afternoon, Harrold said.

Lake Havasu City police issued an Amber Alert for the children early Sunday and traced the alleged gunman, 26-year-old Brian Diez, to the Rancho Cucamonga, Calif., residence of his sister several hours after the shooting.

At about the same time, San Bernardino County Sheriff's Department deputies were sent to the Rancho Cucamonga home about a reported suicide. Deputies discovered Diez dead of a self-inflicted gunshot wound at about 3:30 a.m., authorities said.

The two children — a 4-year-old and a 13-month-old — were found unharmed at the house, police said.

Rancho Cucamonga is about 250 miles away from Lake Havasu City.

Ashley Nyland was a friend of Langstaff's, and Russell and Deborah Nyland are Ashley's parents, Harrold said. Kelson was Ashley Nyland's boyfriend, he said.

Diez fathered the two children with Deborah Langstaff during a long-term relationship, but the couple had been estranged, Lake Havasu City police said.

Langstaff, a nurse at a local hospital, took out a restraining order earlier this year that prohibited Diez from seeing her or the children after he was accused of slapping their infant son, Harrold said.

Diez violated the order Aug. 13 when he approached Langstaff and talked to her, Harrold said. Diez didn't make any threats during the encounter, he said.

Lake Havasu City lies on the shores of a lake formed from a Colorado River dam built in 1938. The city of about 52,000 is perhaps best known as the home of the relocated London Bridge and as a spring break destination for college students.