The gunman who shot and killed six people at a Colorado Springs birthday party on Sunday before turning the weapon on himself was angry about not being invited, police revealed Tuesday. The gunman has been identified by police as Teodoro Macias, Jr. Macias, 28, had been dating Sandra Ibarra, one of the victims, for about a year, said Lt. Joe Frabbiele of the Colorado Springs PD at a press conference on Tuesday. The other five people killed were identified as Melvin Perez, Mayra Perez, Joana Cruz, Jose Gutierrez, and Jose Ibarra. There were 10 people at the home when Macias showed up and opened fire, including three children aged 2, 5, and 11, said Frabbiele. One family member was able to escape the residence during the incident.

“He just showed up, entered the mobile home, and started shooting,” said Police Chief Vince Niski. Frabbiele said that in addition to Macias being upset about not getting an invite to the party, the 28-year-old had been controlling of Ibarra during their relationship, and tried to isolate her from her family. Although police said they consider domestic violence to be “at the core” of the mass shooting, there had been no previous reports of domestic violence between Macias and Ibarra, according to Frabbiele, who said Macias did not have a criminal history. The 9mm handgun Macias used in the brutal slayings was purchased legally from an area gun shop in 2014, said Frabbiele, although Macias was not the original buyer.