<human>: I was riding the subway to work when I noticed some sort of altercation going on in the seat behind me. Through my headphones I heard someone say "Get a life. Get a job." and an inaudible snide retort. As the train slowed to the next stop, I turned around just in time to see a tall, skinny guy, maybe 30 years old, with tattoos full-on punch the old man sitting behind me. The kid immediately got off at the stop we had been slowing to and I gave chase. I don't even know what I was thinking, other than that I would follow him as long as I could and flag down any law enforcement I came across. I was dumb about it, because as I was following him out of the station I made him aware that I was following him by shouting angry expletives. I should have just followed quietly. Hindsight. Anyway, as we were going up the escalator out of the station he stopped and turned around to look at me fully. He got right in my face and said, "You know, you are gorgeous, and this is XXXX station. You better watch it. There are a lot of gang members around here". I said nothing back. When we were out of the station, and I could use my cell phone I immediately called 911. When he noticed, he bolted into traffic and I gave chase. I followed him, at a run, for about 6 blocks while giving descriptions of our location and his appearance to the 911 dispatcher. Eventually I lost him around a corner, but not before the patrol car had caught up with us and I was able to point them down the street where he had disappeared. 

In retrospect, it was really stupid what I did. I could have been seriously hurt. If this guy was OK with punching an old man, then he could have just as easily hurt me the same way or worse.

Give me a shortened version of the text
<bot>: Saw a guy punch an old man on the subway. Chased guy 6 blocks before I lost him. Feeling pretty stupid right now.