The whole gang thing hasn't been around for years. I understand that there still might be a few, but it isn't as nearly as prevalent as it was in the 70s. There is a huge competition in Harlem every year and they have some of the best taggers from around the world, and my friend saw it last year he said it was simply amazing. I think on old abandon buildings or other abandon/some alleyways it is pretty legit. Only, if they are good. They are some cats around here who just suck and ruin the side of buildings. But, on some of the trains I've seen there has been masterpieces.
I still don't think you should be afraid, though. Gang wars or not. Maybe if you are at the park in middle of the night, but if it's not in a bad area it was probably just some high school kid fuxing around.
And if you get caught you are screwed. Cause than they figure out who you are, and you get fined for each tag you made. I had a friend who got caught and was fined $20,000 dollars or something around that cause he had tagged a lot of stuff!!
Keep it lit.