INNEAPOLIS (AP/WGN) — The shooter who killed two Catholic school students and wounded more than a dozen youngsters sitting in the pews of a Minneapolis church once attended the same school and was “obsessed” with the idea of killing children, authorities said Thursday.

The shooter fired 116 rifle rounds through stained-glass windows while the children celebrated Mass during the first week of classes at the Annunciation Catholic School, said Minneapolis police Chief Brian O’Hara.

“It is very clear that this shooter had the intention to terrorize those innocent children,” O’Hara said.

Acting U.S. Attorney Joe Thompson said videos and writings the shooter left behind show that the shooter “expressed hate towards almost every group imaginable.”

The only group the shooter did not hate was “mass murderers,” Thompson said. “In short, the shooter appeared to hate all of us.”

Investigators recovered hundreds of pieces of evidence from the church and three residences, the police chief said. They found more writings from the suspect, but no additional firearms or a clear motive for the attack on the church the shooter once attended. The shooter had a “deranged fascination” with mass killings, O’Hara said.

“No evidence will ever be able to make sense of such an unthinkable tragedy,” he said.

Surveillance video captured the attack and showed the shooter never entered the church and could not see the children while firing through windows lined up with the pews, the police chief said.

Two children, ages 8 and 10, were killed. City officials on Thursday increased to 15 the number of wounded children — ages 6 to 15 — in addition to three parishioners in their 80s who were also injured. Most were expected to survive, O’Hara said.

One child was in critical condition on Thursday, while 11 other victims remained in hospitals.

The shooter, whose mother worked for the parish before retiring in 2021, left behind several videos and page upon page of writings describing a litany of grievances. One read: “I know this is wrong, but I can’t seem to stop myself.”

O’Hara said the shooter was armed with a rifle, shotgun and pistol, and died by suicide.

On a YouTube channel, videos that police say may have been posted by the shooter show weapons and ammunition, and list the names of mass shooters. What appears to be a suicide note to family contains a confession of long-held plans to carry out a shooting and talk of being deeply depressed.