It’s probably been written here, but I didn’t read all of the posts, but the video of the shooter shows he used a suppressor on his pistol. Most people think a suppressor is the same as a silencer. This is not true. Suppressors really do not act as a silencer that we see on TV and in the movies. In some cases, a suppressor will quiet the shot, but not completely.
I have yet to see a suppressor that really fully quiets a shot. I have one that I keep in my safe, but other than taking it to the range, I have never had to use it thankfully.