The gunman who went rouge killing six people and later himself at a Colorado birthday party over the weekend was upset for not being invited.
Police say Teodoro Macias, 28, fatally shot his girlfriend, Sandra Ibarra-Perez, 28, and five relatives before turning the gun on himself.
The attack unfolded at the Canterbury Mobile Home Park in Colorado Springs on Sunday. The party was for three relatives, two of whom died.
The attack came less than two months after a mass shooting that left 11 dead at a grocery store in the north-central Colorado city of Boulder.
Police say the Colorado Springs gunman had a “conflict” with the targeted family at a separate event about a week earlier.
“At the corner of this horrendous act is domestic violence,” the Colorado Springs Police Chief Vince Niski told a news conference on Tuesday.
He added: “When he wasn’t invited to a family gathering, the suspect responded by opening fire.”
He said the killer had “displayed power and control issues”, and had been in a relationship with his girlfriend for about a year. He had no criminal record.
Three teenagers left the party to get an item from a neighbour shortly before the shooting unfolded and returned to the trailer after the attack, police Lt Joe Frabbiele told reporters.
Three children, aged two, five and 11, witnessed the shooting, and were not physically harmed, said police. Seventeen bullet casings were found in the mobile home.
Nubia Marquez, the sister of Melvin Perez and the daughter of Joana Cruz, told the Colorado Springs Gazette the trio had shared the same birthday week and “had always liked celebrating them together”.
She attended the party at the Cruz family trailer park home with her husband, Freddy Marquez.
But the couple told reporters they left around around 10pm on Saturday night.
The shooting took place shortly after midnight, in the early hours of Mother’s Day.
Police said the semi-automatic pistol was not legally owned by the attacker.