Police have identified the suspect who they say opened fire outside of a church at a Catholic school in Minneapolis, killing two children and injuring 17 others, as 23-year-old Robin Westman.

An 8-year-old and 10-year-old were shot and killed when the gunman fired through the windows of a church at the Annunciation Catholic School on Wednesday morning, police said.

Department of Homeland Security Secretary Kristi Noem also confirmed the identity of the suspect, calling Westman a “deranged monster.”

“This level of violence is unthinkable. Our deepest prayers are with the children, parents, families, educators, and Christians everywhere. We mourn with them, we pray for healing, and we will never forget them,” Noem said in a statement.

Driver’s license information reviewed by ABC News describes Westman as a female, born on June 17, 2002.

A name change application for a minor born on the same date 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.”

Police said Westman is believed to be the only suspect in this shooting. Westman does not appear to have an extensive or known criminal history, police said.

Officials said they are looking through information left behind to “try to determine some type of motive” for this shooting. No explosives were discovered at the scene, but a “smoke bomb” was located by officials, police said.

Annunciation church shooting suspect Robin Westman’s mother worked at the church until 2021, according to online posts from the church. Westman also previously attended the school, the police chief told Minneapolis ABC affiliate KSTP.

“We believe he had been a student here, that his mom had worked here in the past,” O’Hara told KSTP.

Mother worked at the church

In the name change application from 2020, Mary Grace Westman was listed as Robin Westman’s mother.

An August 2021 post by the church, reviewed by ABC News, announced Westman’s retirement after five years of service at the church.

A 2020 post by the church’s outgoing pastor described Westman as a parish secretary; a 2016 church bulletin announced her hiring as an administrative assistant in the church’s business office.

Officials looking into YouTube videos

Officials are investigating a series of videos posted to YouTube believed to be associated with Westman, according to law enforcement sources familiar with the matter.

Two videos, posted Wednesday morning and since removed by YouTube, show someone flipping through dozens of pages of notes dated over the course of several months, which include what appears to be doodles of weapons, middle fingers, and expletives. There are also repeated references to killing.

The videos, which depict handwritten journals and a display of high-powered weaponry, paint a portrait of a person with a rambling and deeply nihilistic outlook, according to analyses by law enforcement and ABC News.

The writings in the notebooks and on the firearms, which are written in a blend of Cyrillic alphabet, English and other languages, indicate a series of grievances, anger and ideations of harm to self and to others.

The writings also appear to show overt references to other high-profile school shootings and shooters.

In one notebook, there is a sticker that says “defend equality” with an LGBTQIA flag, overlaid with a gun. A gun also has writings against Israel.

Taking up a full page of a notebook is a hand-drawn birdseye view of the inside of a church with pews. The drawing appears to show the interior layout of Annunciation Church.

In one of the videos the shooter refers to personal depression and apologizes to family members.

YouTube did not respond to a request for comment from ABC News.

Westman died at the scene from a self-inflicted gunshot wound, Minneapolis Police Chief Brian O’Hara said.

The suspect approached the side of the building and fired the rifle through the church windows toward the children and other worshipers sitting in the pews, O’Hara said. Westman was armed with a rifle, shotgun and pistol, and police believe the shooter fired from all three weapons. Police said Westman bought the weapons lawfully and they were “purchased recently.”

Additional firearms are also being recovered from the residences that are “related to the shooter,” police said.

O’Hara described the suspect as a “coward” and said the shooting was a “deliberate act of violence” that is “absolutely incomprehensible.”

“This kind of evil should never happen,” Minneapolis Mayor Jacob Frey 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.”

ABC News’ Katherine Faulders, Aaron Katersky, Josh Margolin, Luke Barr, Mike Levine, Sasha Pezenik and Megan Christie contributed to this report.