An assailant on Wednesday fired through the windows of a Catholic church in Minneapolis, killing an 8-year-old and a 10-year-old and injuring 17 others, the police said.

The attacker then died of a self-inflicted gunshot wound, the Minneapolis police chief, Brian O’Hara, said at a news conference. Of the 17 people injured, 14 were children.

The authorities have identified the attacker as Robin Westman, 23, who is believed to be a former student at the school, according to a law enforcement official with knowledge of the investigation. The F.B.I. is investigating the shooting as an act of domestic terrorism and a hate crime targeting Catholics, Kash Patel, the agency’s director, said on social media.

The police have not yet determined a motive. The suspect’s social media accounts contain videos of diary entries that describe the killing of children and a drawing of the church’s sanctuary. The videos also show weapons, bullets and what appear to be explosive devices.Here’s what we know.

When did the attack happen?

The shooting took place at about 8:30 a.m. at Annunciation Catholic Church in south Minneapolis, which has a school for children in prekindergarten through eighth grade. The students had been observing an all-school Mass, an annual tradition for the new academic year, which began Monday.

Witnesses described harrowing scenes inside the church. Ellie Mertens, a 25-year-old youth minister who said she had been sitting in a pew with children, said that bullets came ripping through a window, and that the school’s principal instructed everyone to get down. The shooting lasted for about two minutes, she said.