Six people were killed at a birthday party in Colorado Springs early Sunday after a man opened fire inside a home before taking his own life.

An unidentified suspect drove to the party, located at a mobile home community, entered the residence where people were gathered and began shooting at around 12:18 a.m., according to Colorado Springs Police. He is believed to be the boyfriend of one of the victims, based on a preliminary investigation.

Children who were at the party were unharmed and are in the custody of family members, police said.

Colorado Springs Police Chief Vince Niski said officers and investigators working the case are “left incredibly shaken.”

“This is something you hope never happens in your own community, in the place that you call home,” Niski 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.”

Authorities found six people dead at the scene and a man seriously injured when they arrived on scene. That man later died at a hospital. The victims have not been identified.

It was a “senseless act of violence” that has left the community mourning, Colorado Springs Mayor John Suthers said.

“We ask the public’s patience with the investigation and we seek the sensitivity of our media partners as CSPD completes a thorough investigation to provide answers to the families and friends impacted by this tragedy,” Suthers said in a statement Sunday.