A military impostor is a person who makes false claims about their military service in civilian life. This includes claims by people that have never been in the military as well as lies or embellishments by genuine veterans. Some individuals who do this also wear privately obtained uniforms or medals which were never officially issued to them.
Lying about military service or wearing a uniform or medals that were not earned is criminalized in some circumstances, especially if done with the goal of obtaining money or any other kind of tangible benefit, though laws vary by country. In the United States, any person who commits the crime of stolen valor shall be punished by imprisonment in a house of correction for not more than 1 year or by a fine of $1,000, or both such fine and imprisonment.
Who did this guy think he was fooling? If you’re going to cosplay as a military person you should probably at least get the uniform right.