COLORADO SPRINGS, Colo. (AP) — Colorado authorities are investigating why a gunman opened fire at a weekend birthday party, killing his girlfriend and five other adults inside a house trailer before killing himself. Police say the shooting happened just after midnight on Sunday in Colorado Springs. The Colorado Spings Gazette reported that oficers arrived at a home trailer to find six people dead and a man with serious injuries who died later at a hospital. Police say the suspected shooter was the boyfriend of a female victim at the party attended by friends, family and children. He walked inside and opened fire before shooting himself. No children were hurt.