Texas isn't listed as one of the States where LEOs are authorized to carry the .45GAP line of handguns. So I'd guess the cop used a Glock 21 firing standard .45 rounds. Probably has a nicer recoil anyway, and for a holstered duty weapon the size difference wouldn't matter as much.
That, and he's probably put a million practice rounds through it... LOL!
Yep, and he saved many lives.
Probably a handloader too. (grin)