Soldato
The light bouncing off the man's body/clothing/weapon would travel from him to my eyes, the light would then travel through my outer eye and be projected onto my retina. After which my retina would send these signals to my brain, my brain would then process the raw images and then interpret them. The most likely outcome would be that my brain would first already know that I was in the shop and then recognise the shapes corresponding to the man and I would recognise him as a man. Secondly my brain would most likely discern that the weapon was in fact a weapon and at that point it would probably be a concious though process to identify the weapon make/model.