I searched for and looked at the video the OP mentioned. The one I looked at was only about 35 seconds long and showed that particular photo and another one with the same great clarity with what looked like the same pistol on the ground at the rear of a van. At first I thought CZ-82 for some reason, but does kind of look like a Beretta Tomcat in that other picture.
The video is by Gavin Fish, and it's maybe 20 mins. I did a zoom and it looks to me like the barrel is round instead of with flattened sides and has no lug under it, so I figure it might be a flare gun. It doesn't look like a Tomcat nor a CZ-82.
Also, it's from her Instagram account, verified by Gavin Fish, who's a serious true crime buff.