Subject: Bullet casings
The fired bullet casing contained the inscription, "Notices bulges OwO what's this?"
An unfired bullet casing read, "Hey fascist, catch!"
And a second unfired casing read, "oh bella ciao, bella cio, bella ciao, ciao, ciao."
A third unfired casing said, "If you read this, you are gay."

Inscriptions on the three unfired casings read
‘Hey, fascist, exclamation point, catch, exclamation point.
Up arrow symbol, right arrow symbol and three down arrow symbols,’

Clearly the shooter thought Kirk was a fascist. And provides a motive.

Still not sure what "Notices bulges OwO what's this?" means. It's meme from online gaming apparently.