Anything would have got his attention.
It’s like throwing a 1200 to 1500 fps brick at him.
The armor may stop penetration, but that jasper would be rattled enough to throw him of his game.
And then again who ever popped him first could be the next to go down, drawing attention to themselves.
But body armor won’t protect you indefinitely.
My “everyday” weapon comes in 9mm, I was thinking my SIG would be better than nothing in the situation but if those plates were level-4 wouldn’t a 9 just bounce off?