A man apparently upset over a family business dispute "snapped" before fatally shooting his two brothers, his mother and his sister-in-law and then killing himself at a home in Phoenix, police said on Friday.
The shooter was found by police in an upstairs bedroom with a self-inflicted gunshot wound after Thursday's incident, said Sergeant Trent Crump, a Phoenix police spokesman.
The victims all suffered multiple gunshot wounds in what police described as a blood-splattered crime scene. The victims and gunman were aged between 28 and 75, Crump said. None of them are so far being named by police.
"Things weren't going well between them (the brothers)," Crump said.
Crump said witnesses described how one of the brothers "snaps or loses it." He said the man apparently killed his brothers downstairs, before shooting and killing his mother when she arrived at the house to see what was happening.
He then went upstairs and fatally shot his sister-in-law before turning the gun on himself, investigators said.
"It's very obvious that whether it was the heat of passion of the moment or the anger of what happened he certainly went to great lengths to make sure that each of them were dead," Crump told a news conference.
The suspect's wife and two children, 11-month-old and 3-year-old girls, escaped through a downstairs sliding glass bedroom door, Crump said.
A female relative was also able to flee about an hour after the shootings, Crump said, and told investigators the incident had escalated from an argument over a family business.
Police said the family owned businesses including a transport company and several restaurants.
(Reporting by David Schwartz; Editing by Daniel Wallis and Will Dunham)