Transgender mass shooter Robin Westman blindly fired over 100 rifle rounds and at least three shotgun blasts through the windows of Annunciation Catholic Church after being unable to enter through the locked exterior doors, Minneapolis Police said in an update Thursday.

Minneapolis Police Chief Brian O’Hara said the church’s practice of locking doors during Mass “without a doubt” saved additional lives, preventing Westman from getting a clear line of sight to his child victims — who Acting US Attorney for district of Minnesota Joe Thompson said the deranged gunman “wanted to watch suffer.”

“More than anything, the shooter wanted to kill children. Defenseless children,” Thompson said at the afternoon press conference, adding that the Westman’s “heart was full of hate.”

Two children were killed in the cowardly mass shooting, which unfolded Wednesday morning as the church was packed with children for a celebratory back-to-school Mass. There were also 18 injured victims, 15 of them children, police said Thursday — one more injured child than was reported Wednesday.

Here's what we know about the Catholic school shooting in Minneapolis

• Students had begun their first week of school at the Annunciation Catholic School in Minneapolis, Minnesota, two days before the shooting.
• Robin Westman, a 23-year-old trans woman, opened fire through the stained glass windows on Wednesday morning during a celebratory back-to-school Mass filled with children.
• The shooting killed two children and injured at least 18 others, before Westman died of a self-inflicted gunshot wound.
• Westman had written “Kill Donald Trump” and “for the children” on gun magazines, and posted videos of a handwritten manifesto.
• Westman’s mother had worked at the school.

The young victims’ injuries ranged from “graze wounds” to “some very serious life-threatening injuries,” including some who are “very seriously injured and in critical condition.”

O’Hara said investigators recovered three spent shotgun shells, 116 rifle rounds and a single bullet from a live handgun “that appears to have malfunctioned and got stuck in the chamber” of his weapon.

So far “hundreds” of pieces of evidence including electronic devices have been recovered from three local addresses known by authorities to be connected to Westman, all of which were visited by police bearing search warrants after the broad-daylight attack.

“We are doing our best to determine a specific motive. But the purpose of the shooter’s actions was to obtain notoriety,” O’Hara said, noting that Westman was not previously known to law enforcement, including any state-ordered mental health commitments.

Churches and schools in Minneapolis will see stepped up police presence in the coming weeks, particularly as schools start to open for the year.