Mourners organize a memorial, Monday, May 10, 2021, outside a mobile home in Colorado Springs, Colo., where a shooting at a party took place a day earlier that killed six people before the gunman took his own life.

COLORADO SPRINGS, Colo. — A man who fatally shot six people at a Colorado birthday party before killing himself was upset after not being invited to the weekend gathering thrown by his girlfriend's family, police said Tuesday.

The shooter, 28-year-old Teodoro Macias, had been in a relationship with one of the victims, 28-year-old Sandra Ibarra, for about a year and had a history of controlling and jealous behavior, Colorado Springs police Lt. Joe Frabbiele said at a news conference.