A Shooting in Minnesota

Minneapolis is in mourning after a shooter opened fire at a school Mass marking the start of the academic year. “We are a city united in grief,” Jacob Frey, the mayor, told a crowd at a candlelight vigil. “Let us take the next step to be a city united in action.”

The shooting at Annunciation Catholic Church, in the south of the city, lasted about two minutes. It took the lives of two children and wounded more than a dozen people.

Children and staff members ducked for cover under the pews, witnesses said, as the assailant fired into the church through the stained-glass windows. At least two doors of the church had been barricaded from the outside, the police said. The attacker later shot herself.

The F.B.I. is investigating the shooting as an act of domestic terrorism and a hate crime targeting Catholics. Here’s what else to know:

The victims: The attack killed two children, ages 8 and 10, who died in the pews of the church. At least 14 other children, between the ages of 6 and 15, were wounded, as were three parishioners in their 80s.

The suspect: The authorities identified the attacker as Robin Westman, a 23-year-old who they believe was a former student at the school. The shooter was armed with three guns, all of which had been legally purchased.

The motive: Investigators said they had not determined a motive. The suspect’s social media posts show a fixation on guns, violence and school shooters. Videos she posted featured diary entries that described the killing of children and a drawing of the church’s interior.