At least two children were killed, and 17 others were injured in a shooting that occurred Wednesday morning during the first week of classes at a Minneapolis Catholic school.

The shooting happened during Mass at Annunciation Catholic School. Monday had been the first day of classes. Of the 17 injured, police said 14 were children. Two of those children were in critical condition.

The two children who were killed were 8 and 10 years old, officials said. Authorities have not released the identities of the victims, but said the children who were killed were fatally shot while they were in the church pews celebrating Mass.

It is unclear how many people were inside the church at the time.

Minneapolis Police Chief Brian O'Hara said the shooter - armed with a rifle, shotgun and pistol - approached the side of the church and shot through the windows toward the children inside before killing himself in the parking lot.