The memes havent caught up yet. They actually found casings for the full book title "Delay Deny Defend" and the shooter additionally carved the "Depose" on one of the casings as the final conclusion to this phrase.
Tbh the articles might just be wrong about one of the words, but together these two articles used as source for the wikipedia article contain all the mentioned words.
Dont worry about it, i was just being pedantic because lots of news outlets are still calling the reference to the book a "maybe" which is annoying because everything about this shooting is as clear as day.
This is a weapons expert with experience with both of the types of weapon you're talking about and he says it's definitely not a VP9 or a welrod. https://youtube.com/shorts/POubd0SoCQ8
He pointedly makes no comment on all the people celebrating.
A lot of people in the comments seem to agree that this guy probably knew the gun wouldn't cycle and was expecting to clear malfunctions, which is why he seems unbothered by them. He may not have had access to legal and proper methods of suppression, hence the poor setup. Probably for the best because a registered suppressor would be easily traced.