I think they believe the gun was a B&T VP9. It is a pretty oddball gun, and because if it’s unique design with an integrated wiper based suppressor they are EXTREMELY quiet, but a bit inaccurate as the wipers contact the bullet on its way out. Paired with some subsonic ammo, this gun would be move style quiet and you probably wouldn’t think twice about hearing the noise it makes on a busy street. Either that or a gun hand built to a similar design. It sure seems to operate like a vp9 the way it’s single shot and by the manner he cycles the gun after each shot.