Think it is very unlikely it was a .45 GAP round, The G21 is a pretty popular .45 ACP pistol.
...and I want to echo the willingness to buy the officer the drink of his choice. I would deliver a bottle of Macallan 25 to the Garland Police Department.
I would hope that officer never pays for another drink for the rest of his life.
I agree. I was just pointing out that it was a Glock and not a 1911. Glocks get a lot of snorts around here, so I had to take advantage of the opportunity : )