The man who fatally shot six people at a Colorado birthday party was upset he wasn't invited to the gathering, police say

• The police say a man killed six people at a Colorado birthday party Sunday before shooting himself.
• Authorities on Tuesday said he was upset he didn't get an invitation to the party.
• One of the victims was identified as the man's girlfriend, and he was described as "controlling."

The man who opened fire at a birthday party in Colorado Springs, Colorado, and killed six people was upset he wasn't invited to the party, the police said.

Investigators identified the shooter as Teodoro Macias, 28, who they said was dating Sandra Ibarra, one of the six victims, for about a year and was angry over not being invited to the gathering.

"When he wasn't invited to a family gathering the suspect responded by opening fire and killing six victims before taking his own life," Chief Vince Niski of the Colorado Springs Police Department said during a press conference Tuesday.

Lt. Joe Frabbiele said Macias was characterized as a controlling and jealous boyfriend.

"At the core of this horrendous act is domestic violence," Niski told reporters. "The suspect, who was in a relationship with one of the victims, displayed power and control issues in this relationship."

Frabbiele said Macias tried to isolate Ibarra from her family and tried to prevent her from attending family events.

No domestic-abuse police reports were filed between the two, Frabbiele said.

The shooting occurred after midnight on Sunday at a mobile home where families related by marriage were celebrating a birthday.

Police officers arrived at the scene after being called about a shooting and found six people dead and one man who was seriously injured and later died at a hospital.

The police said there was evidence that children ages 2, 5, and 11 witnessed the shooting, though none were injured.

"Today we find ourselves mourning the loss of lives and praying solemnly for those who were injured and those who lost family members in a senseless act of violence on Sunday morning," Mayor John Suthers of Colorado Springs said in a statement on Sunday. "We think too of the emergency personnel who responded to a horrific scene and we keep them in our prayers today."

The police identified the six victims as Sandra Ibarra, Jose Ibarra, Mayra Ibarra de Perez, Melvin Perez, Jose Gutierrez, and Joana Cruz.