Reid’s gun

Please excuse my terrible knowledge of firearms but can anyone tell me why Reid has such a different looking gun from the usual ‘cop’ ‘police’ etc type of gun the others have? To me, it looks like an old timey type gun with a barrel…? Is this normal for USA FBI?? As in, you can choose what you use? Where I am from, most police have the exact same gun unless they are riot squad or responding to something hectic. Sorry if this has been asked before also xx