Authorities are probing two main threads in the investigation into the Minneapolis school shooting that left two students dead and 21 others injured.

According to U.S. Attorney Joe Thompson, officials are working to confirm, as they believe, that the shooter acted alone. They're also working to establish a motive.

At a press conference Thursday afternoon, Thompson described how the shooter left behind hundreds of pages of writings and plans that delved into their mental state and "pure, indiscriminate hate."

"The shooter expressed hate towards almost every group imaginable. The shooter expressed hate towards Black people. The shooter expressed hate towards Mexican people. The shooter expressed hate towards Christian people. The shooter expressed hate towards Jewish people. In short, the shooter appeared to hate all of us," Thompson said.

He went on to describe that there was "one group that the shooter didn't hate. One group of people who the shooter admired."

"The group were the school shooters and mass murderers that are notorious in this country," Thompson said, refusing to name any specific examples in order to keep them from receiving any more attention.

The shooter fired through the windows of Annunciation Catholic Church during Mass around 8:30 a.m. Wednesday, according to Minneapolis city officials. Police recovered three shotgun shells and 116 rifle rounds at the scene.

Of the 21 injured, all but three were children. The three injured adults were all parishioners in their 80s, Minneapolis Police Chief Brian O'Hara said Wednesday afternoon. 

Injuries range from a "graze" to "serious, life-threatening injuries," O'Hara said. All the injured are expected to survive.

Minneapolis police executed four search warrants Wednesday: one at the church and three at various residences tied to the shooter. Police recovered "literally hundreds" of pieces of evidence including electronic devices. No additional firearms were found, O'Hara said. The three firearms that were found at the church were all purchased legally.

The shooter previously attended Annunciation Catholic School, and their mother was a previous employee who retired in 2021, according to a Facebook post from the church. Police have not yet been able to interview the mother, O'Hara said Thursday.

Authorities haven't been able to pinpoint a "triggering event" or a "specific grievance" that spurred the attack, according to O'Hara.

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