Robin Westman, the male-born transgender individual who killed two people in a church shooting at a Minneapolis Catholic school on Wednesday, visited the church weeks before the attack, a senior law enforcement official told CNN.

Armed with a rifle, shotgun and pistol, Westman, 23, shot dozens of rounds Wednesday morning toward children sitting in the pews during Mass at Annunciation Catholic School, Minneapolis Police Chief Brian O'Hara said. The shooter then died by suicide, he said. Two children were killed and 17 other people were wounded.

Westman intended to carry out the shooting from inside Annunciation Church, with the goal of inflicting many more casualties among the children targeted, authorities told CNN.

The shooter visited the church under the pretext of reconnecting with his Catholic faith at the school, which he previously attended, CNN reported, citing investigators.

From his church visit, Westman, who changed his name from Robert in 2020, created a detailed, hand-drawn diagram of the church's interior that was shown on a video he intended to publish on YouTube. Westman was unable to enter the church Wednesday because doors were locked after Mass started, likely saving many lives.

"A number of the doors had been locked once Mass began, which is part of their normal procedure," O'Hara told CNN. "We believe that this step also played a part in ensuring this tragedy did not become that much worse."

In another video Westman intended to post, it shows wooden boards with smoke canisters attached, which he intended to place through the door handles of the emergency exits so students would be trapped inside, officials told CNN. Had he entered the church, the victims who fled to emergency exits would find themselves trapped and the room filled with orange smoke, CNN reported.

Westman was instead forced to fire through the windows of the church.

• Grossman to Newsmax: Schools Need Tools to Defeat Gun Violence
• Minneapolis Police Chief to Newsmax: Shooter's Mother Difficult to Reach