(MINNEAPOLIS) -- An 8-year-old and 10-year-old sitting in pews were killed when a shooter fired shots through the windows of a church at the Annunciation Catholic School in Minneapolis on Wednesday morning, police said.
Seventeen others were injured in the shooting during a Mass that marked the first week of school, Minneapolis Police Chief Brian O’Hara said.
Fourteen of the injured victims were children ages 6 to 15, and the three adults who were shot were parishioners in their 80s, he said. Two children are in critical condition, police said. All of those injured are expected to survive, O'Hara said.
The shooter died at the scene from a self-inflicted gunshot wound, O’Hara said. The FBI identified the shooter as 23-year-old Robin Westman, who was born Robert Westman.
Driver's license information reviewed by ABC News described Westman as a female, born on June 17, 2002. A name change application for a minor born on the same date, June 17, 2002, was approved by a district court in Minnesota in 2020, changing the name of a Robert Westman to Robin Westman, explaining the minor child "identifies as a female and wants her name to reflect that identification."
The mass shooting unfolded just before 8:30 a.m. when the shooter approached the side of the building and fired a rifle through the church windows toward the children and other worshippers sitting in the pews, O’Hara said.
Dozens of rounds were fired, the chief said, and he called it a "deliberate act of violence against innocent children and other people worshipping."
"Within seconds" of the gunfire, the "heroic staff moved students under the pews," the Annunciation Parish and School said in a statement. The students and staff were evacuated "in a matter of minutes when it was safe to do so," the school said.
The suspect was armed with a rifle, a shotgun and a pistol, and police believe shots were fired from all three weapons, the chief said. All three weapons were purchased legally and recently, police said.
A possible smoke bomb was also discovered at the crime scene, the chief said.
Weston, a 10-year-old fifth-grader at the school, said he was sitting next to a stained glass window the shooter fired through.
"It was right beside me. I was like 2 feet away from the stained glass window. So, the shots were right next to me," Weston told Minneapolis ABC affiliate KSTP.
The boy said he and his classmates immediately hid under a pew as the gunfire continued.
"My friend got hit in the back. He went to the hospital," said Weston, who spoke to KSTP with the permission of his grandfather. "I was super scared for him, but I think he's OK."
He said he and his classmates were taken to the school gym, where they waited for the news of what had just occurred.
Weston said his mother was outside the church when the shooting erupted, and was the first person he saw when he emerged from the church.
"I was scared that I wasn’t going to see her because I didn’t know what was happening. I was just in shock," Weston said.
During a news conference, an emotional Minneapolis Mayor Jacob Frey said, "These kids were literally praying. It was the first week of school. They were in a church. These are kids that should be learning with their friends, they should be playing on the playground. They should be able to go to school or church in peace without the fear or risk of violence, and their parents should have the same kind of assurance."
"This kind of act of evil should never happen, and it happens far too often," he said.
Frey stressed at a second news conference, "Anybody who is using this as an opportunity to villainize our trans community, or any other community out there, has lost their sense of common humanity. We should not be operating out of a place of hate."
"Kids died today," he continued. "This needs to be about them. This needs to be wrapping our arms around these families."
Students in pre-K to eighth grade attend the school. Young children wearing their uniforms were seen leaving the school holding their parents’ hands.
"Minnesota is heartbroken," Minnesota Gov. Tim Walz wrote on social media. "From the officers responding, to the clergy and teachers providing comfort, to the hospital staff saving lives, we will get through this together. Hug your kids close."
Police said they believe the shooter acted alone.
The chief said police are "looking through information left behind to try and determine some type of motive."
The FBI is investigating this shooting as an act of domestic terrorism and hate crime targeting Catholics, Director Kash Patel said.
Law enforcement is investigating social media accounts believed to be associated with the shooter, specifically a video posted earlier Wednesday on YouTube, sources familiar with the matter told ABC News. The video shows someone flipping through dozens of pages of notes, which include what appears to be drawings of weapons and one drawing depicting the inside of a church with pews. The YouTube video has been taken down, the police chief said.
One notebook has a sticker that says "defend equality" with a silhouette of a long gun, and one sticker references a German band that was popular with the Columbine shooters. The band has previously denounced any such violence.
A student at the school told KTSP that she was in the church when she suddenly heard a loud noise that she initially thought was fireworks.
"And then I saw the shooting and I was like, 'Oh my gosh, I'm so scared,'" said the girl, who did not want her name published.
She said a teacher led her and her friend downstairs to seek shelter in a preschool classroom.
"Me and my friend ... were just praying and praying," she said. "I was just like praying everybody could be safe and like nobody would do this again."
Yusef Davis told KSTP his nephew was shot in the stomach during the shooting and underwent surgery. He said he spoke to his nephew at the hospital after he got out of the operating room.
President Donald Trump wrote on Truth Social that he's been "fully briefed on the tragic shooting."
"The White House will continue to monitor this terrible situation. Please join me in praying for everyone involved!" he wrote.
Trump called Walz after the shooting to offer his condolences, a source told ABC News.
Trump has ordered flags to be flown at half-staff until Sunday.
After the shooting, former President Barack Obama spoke out about gun violence, writing on social media, "We can't allow ourselves to become numb to mass shootings. What happened today in Minneapolis is heartbreaking, and Michelle and I are praying for the parents who have lost a child or will be sitting at their hospital bedside after yet another act of unspeakable, unnecessary violence."
Former President Joe Biden wrote, "Jill and I are heartbroken and there are simply no words to adequately mark such a horrific and painful moment."
"With all our hearts, we are praying for the victims, their families, and the community of Minneapolis," he said.
This is a developing story. Please check back for updates.
ABC News' Pierre Thomas, Jack Date, Luke Barr, Aaron Katersky, Sasha Pezenik and Michael Pappano contributed to this report.