This guy is wrong on a number of things. First of all the "cellphone gun" is not a cellphone at all. There is no screen. Also, I never saw the guy unfold the grip so that it could be fired.

Yes, there is probably another shooter, as in many of these things, but the guy pointed out in the video probably isn't the one. It's just like with Trump, the guy on the roof didn't fire a shot from the roof that nicked Trump's ear and then went upward to kill the man higher up in the stands. I think the real shooter then was inside the building shooting from the door or through a window. There are lots of patsies, at least since Lee Harvey Oswald.