(NewsNation) — The shooter behind the deadly attack on a Minneapolis Catholic school and church that left two children dead and 17 other people injured, Minneapolis Police said Wednesday.

The shooting took place during an all-school mass at the Annunciation School, a private elementary school on the south side of the city.

Shooter is dead: Police

Minneapolis Police Chief Brian O’Hara said the shooter, identified as a man in their 20s, killed themselves in the parking lot outside the church. Authorities have not yet released the identity of the shooter.

“During the mass, a gunman approached on the outside on the side of building and began firing a rifle through the church windows towards the children sitting in pews at the mass,” O’Hara said. “The sheer cruelty and cowardness of firing into a church full of children is absolutely incomprehensible.

Shooter had no criminal record

O’Hara said the shooter, dressed in black, was armed with a rifle, a shotgun and a pistol, adding that he did not have a known criminal history. He added that it is unclear if the shooter was a former student of the school or employee.

“We are looking through information left behind to try and determine some type of motive,” O’Hara said.

What we know about the Annunciation School in Minneapolis

At least five of the injured are children, The Associated Press reports, with a pediatric trauma hospital saying five children were admitted for care.

Classes began on Monday for the school, which serves pre-kindergarten through eighth grade.

This story is developing. Refresh for updates.