Witnesses to a mass shooting in the US city of Minneapolis have described the terrifying scenes after an attacker opened fire on a church in which children were celebrating Mass on Wednesday morning.

One young boy described being protected by a friend who got hit himself.

Two children were killed and 17 others injured in an incident that the FBI is treating as an anti-Catholic hate crime.

The attacker, named as 23-year-old Robin Westman, died at the scene from a self-inflicted gunshot wound. Authorities have not yet given a suspected motive.

Weston Halsne, a 10-year-old survivor, explained how his friend Victor saved him by laying on top of him, taking a bullet to the back. I was super scared for him but I think now he's okay, he stated, revealing they were well-drilled for shooting situations but never imagined such a tragedy could take place in a church.

As reports unfolded, locals described the chaos, with some believing the shots were from construction work nearby until the horror became apparent. Madrigal's mother expressed her mixed emotions of relief that her children were safe yet anger and sadness over the lives lost.

The investigation continues as police seek to understand how the attack unfolded, and community members rally for change in the face of seemingly unending gun violence.