Six people are dead after a gunman entered a birthday party and began shooting inside a mobile home in Colorado Springs, Colorado, USA, before killing himself during the early-morning hours of Mother’s Day, police announced Sunday, The Washington Post reported.

The mass shooting unfolded around midnight Sunday at the Canterbury Mobile Home Park, about eight miles outside downtown Colorado Springs, police said. The gunman, who authorities said was the boyfriend of one of the female victims, has not been publicly identified.

The Colorado Springs Police Department said in a news release that the man “drove to the residence, walked inside and began shooting people at the party before taking his own life.” The shooter’s motive is still being investigated, police said, and the type of firearm used was not specified.

All of the victims, whose names and ages have yet to be released, were adults. One of the victims was the one celebrating a birthday, police said. None of the children at the party were injured, authorities said. The children are now with relatives.

When police arrived at the scene at 12:18 a.m. Sunday, they said they found the male shooter, an adult, who was transported to a hospital with “serious injuries.” Authorities confirmed that he died at the hospital.