Seven people have died after a gunman barged into a birthday party in Colorado Springs before taking his own life.
Investigators believe the killer opened fire inside a mobile home, where his girlfriend was present.
There were children present as the horror shootings happened shortly after midnight, police said.
The shooting happened inside a mobile home, with officers responding to the horror killings "incredibly shaken".
Lt. James Sokolik said in a statement: “He drove to the residence, walked inside and began shooting people at the party before taking his own life.”
"Upon arrival, officers located six deceased adults and one adult male with serious injuries who was transported to a local hospital where he succumbed to his injuries," a statement from authorities said.
Colorado Springs Police Chief Vince Niski said: “Words fall short to describe the tragedy that took place this morning.
"As the chief of police, as a husband, as a father, as a grandfather, as a member of this community, my heart breaks for the families who have lost someone they love and for the children who have lost their parents.
"From the officers who responded to the shooting to the investigators still on scene, we are all left incredibly shaken.
"This is something you hope never happens in your own community, in the place that you call home."
The police chief called on the public for patience, pledging to do everything possible to find out how the horrific shooting happened.
He said: "When these types of unspeakable acts happen, there is nothing that can be done to fully rebuild what was lost or replace those who are no longer with us.
"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 be here for you with an unwavering support.”
Colorado Springs Mayor John Suthers said: “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.
"We think too of the emergency personnel who responded to a horrific scene and we keep them in our prayers today."
