Two children were killed and 17 other people were injured on Wednesday after a gunman opened fire on students who were attending Mass at a Minneapolis Catholic school, authorities said.
The assailant, a man in his early 20s, fired dozens of rounds through the church windows and then took his own life, officials added.
He was armed with a rifle, a shotgun and a pistol.
"This was a deliberate act of violence against innocent children and other people worshipping. The sheer cruelty and cowardice of firing into a church full of children is absolutely incomprehensible," Minneapolis Police Chief Brian O'Hara told reporters.
The shooting occurred two days after school started at Annunciation Catholic school, a private elementary school with about 395 students.
The school is connected to Annunciation Catholic Church, and both are located in a residential area in the southeast part of Minnesota's largest city. Local TV showed parents ducking under yellow police crime tape and leading students out of the school.
Officials said the shooter wore black clothing, was in his early 20s and did not have an extensive criminal history. They did not provide his name and said they were trying to identify a motive.
Children's Minnesota, a local hospital system, said it was treating six children.
There have been more than 140 shootings at US elementary and secondary schools this year, according to the K-12 School Shooting Database.
US President Donald Trump said he had been briefed on the shooting and said the FBI was on the scene. "Please join me in praying for everyone involved!" he said on social media.
The US Department of Homeland Security is in touch with local authorities and monitoring the situation, Homeland Security Secretary Kristi Noem said on social media.
There have been three other shootings in the midwestern city since Tuesday afternoon, including one at a Jesuit high school, that have together left three people dead and seven wounded, according to police.
Wednesday's shooting did not appear to be related to the others, O'Hara said.
Minneapolis has experienced a significant rise in homicides in the years following the 2020 police killing of George Floyd, which prompted nationwide protests, civil disturbances and staffing shortages in the city's police department.
The city recorded 54 homicides last year, down from 71 in 2021 but well above the 29 recorded in 2019.
In June, Minnesota also experienced an incident of political violence, when a gunman posing as a police officer allegedly assassinated a Democratic state lawmaker and her husband in their home, and wounded another lawmaker and his wife.
The suspect was arrested after a massive two-day manhunt and faces state and federal murder charges.
Minnesota state law requires background checks for all gun sales and the state as a whole has a gun death rate below the national average, according to Everytown for Gun Safety, a gun violence prevention group.

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