Here is the still image from the video:

Image

• A muzzle flash normally shows as a “ball” of high pressure hot gas in front of the muzzle. In the image there is no “ball” of light in front of the muzzle. It is the snow on the ground being lit by the light

• There is also the possibility of muzzle glow directly at the muzzle. But the white streak at the front end of the barrel cannot be that because muzzle glow is orange-red, not white and would not last long enough to make a streak on camera because of the movement and exposure time. The muzzle flash would have also washed it out.