What a cop carries is determined by a lot of things. I’d assume that those were the infamous lung-blowing-out 9 mm hollow points. It provides for easy carry of a reasonable number of rounds...15+ in the pistol, and 50 more in spare mags, if the cop is smart. Minus the need for easy portability, as in home defense, rifle calibers in 30 round magazines would deliver more power, to potentially more threats.
Most likely it was the 9mm- I’ve seen other videos of cops hitting suspect nu erous times and the perp keeps coming towards the cop. The left think that bullets are magical and can end life with one shot, and that noone n3eds more than a few shots at best. The left n3ver have our best interests in mind- on,y the criminals best interest