Let's treat it as just as deadly as the police would if you fired it at their car.

Eventually, someone will panic and shoot back, then they'll put away the non-lethal and start killing people, for safety reasons. For examples see any interaction with local police.

Almost certainly pepper balls. I don't know what else it could be. It's something powdered at least, and that's the only thing I know of that acts like that fired out of that weapon.

But yeah, I read the title and assumed gunpowder bullets. It sucks that we're thankful for "only" this level of violence.