Police in Colorado Springs, Colorado are working to determine a motive after a gunman walked into a birthday party inside a mobile home yesterday and opened fire, killing six people and then himself.

“My vow to this community and to the families who have lost someone today is that this department will do everything we can to find you the answers you deserve and to be here for you with an unwavering support,” said Colorado Springs Police Chief Vince Niski.

The name of the gunman and the victims have not been officially released. The shooting broke out shortly after midnight, and responding officers located six dead adults along with one who suffered serious injuries. He later died at the hospital.

There were children inside the home but they were not targeted.

The gunman is believed to be the boyfriend of one of the female victims. He arrived at the party, which was attended by an extended family, and opened fire.

Freddy Marquez, one of the partygoers who left early because his wife had work in the morning, said the guests were all members of the same family.

He said his wife lost her mother and two brothers in the shooting. The children who were at the party are now staying with relatives.

“The tragic shooting in Colorado Springs is devastating,” said Governor Jared Polis, “especially as many of us are spending the day celebrating the women in our lives who have made us the people we are today.”