Thanks for the information Sifu Wallace.
Not sure of the size of the pistol but it looks like the percussion alone knocked the stuff off of the display shelves. It may have knocked him unconcious as well.
Okay, looked at the video again.
Hard to tell from the video the details, but it looked like the clerk got off two shots. The first shot might have hit the perpetrator in the thigh or leg, and passed through the body, but it looks more like it missed. The round penetrated into the far left 2-liter bottle on the second shelf. There is a fairly good explosion from hydrostatic shock and liquid is seen leaking out of a hole from the bottle after the shot.
It looks like the second round penetrated the perpetrator under the right armpit, about as low as on the side of the floating ribs. A round there could shatter a rib and you can get a lot of internal damage plus the effects of a hollow-point could be like a half-dozen tiny daggers penetrating into tissue. The brain response to trauma is to shutdown, I know a good hit there has made my whole body want to collapse just from a kick or a punch, especially a one knuckle punch. I can't imagine how much worse a bullet would be. Also, when shot or shot at, human psychology can be to go down, even on flesh wounds that can happen.
I'm not sure if the perpetrator did not get up and run away, but this isn't shown in the video. At the end of the video, which is about a minute after the shooting, the clerk appears to be looking for someone and points his gun at something while on the phone. Not sure what is going on there but it could be the perpetrator running away.
As for the firearm, it resembles a Beretta PX4 Storm pistol. This model comes in 9 mm and .40 S&W. The .40 S&W would pack a much bigger punch than the 9mm version.