Can a civilian be considered a "snitch?" If so, when? No, because there a civillian. They never signed up for the lifestyle as criminals agree to as far as "no snitching". But people that are criminals get that confused IRL and IG. So they probably would label you as a snitch. It's all a IC / IRL matter.
Does calling fire / ambulance also fall into this territory? Um.. No, unless your calling to have that person in trouble of some sort.
Do you think gangs targeting these people would bring more "heat" from the police? Obviously?