A heavily armed shooter opened fire Wednesday on schoolchildren attending a church service in Minneapolis, killing two pupils and wounding 17 people in the latest violent tragedy to jolt the United States.

Minneapolis City Police Chief Brian O'Hara said that the attacker sprayed bullets through the windows of the Annunciation Church as dozens of young students were at a Mass marking their first week back at school.

The church sits next to an affiliated Catholic school in Minneapolis, the largest city in the Midwestern state of Minnesota.