"I could have been somebody": The other Mark

I have never seen and will never again see someone put an Olde English 24oz can away with the speed and determination of Mark. One long chug, spit out the foam, chug the rest. I counted once. 7 seconds. Impressive and depressing at the same time.
I first met Mark probably on my first day. He would be the first one in at 8 AM(sometimes earlier on accident) to get his beer. He only ever drank OE800(this is important to remember later on) Always. He would also use the store as a grocery store, which always bums me out to see as we are a convenience store, so we don't offer that great a selection of healthy food. He would rarely wash his clothes, and I could only assume lived in squalor, because he would constantly buy Glade air freshener(air spray as he called it, which always caused confusion as to why he needed it, he was bald, and we were hearing hair spray over the phone). I always felt bad for the guy, except the few times he sliced OE cans open on the sharp edge of the slot they're in and then just stood there holding it saying "Hey boss man, I think this one's leaking." as it sprayed everywhere. Those times, I loathed him.
Mark was pretty blind, I don't really know how well he could see. He would walk around most of the day looking for partial cigarettes on the ground, I witnessed him smoking filter on multiple occasions. He had a child's sock that he would keep his change in, and it always took him forever to get his change out or put it away, and if he dropped change, strap in, because he's going to be there for a while crawling around looking for it, I would get frustrated at that as well.
Most of the time he was pleasant enough. About a year into me working here he just one day, all of the sudden, blurted out "Man, I could have been somebody", I just stood there and looked at him, puzzled. How the fuck am I going to respond to that? I said "Yeah, well..." and that was that. It was probably the most powerfully sad interaction i have had yet with a customer.
We have a policy that if we ban a customer(there are a lot of banned customers, mostly for getting belligerent and mean when they're drunk, so we don't want to be the ones to facilitate that kind of behavior in the neighborhood) you cannot come in and buy anything for them, if we find out that you are, you risk being banned yourself. Mark came in one day, probably about 6 months ago, and bought a 6 pack of Genesee 16oz cans. Mark doesn't drink Genesee, ever. I had known that man, pretty well, for over 2 years at that point. I said to him, flat out "Mark, you don't drink Genesee, you aren't buying this for someone who isn't allowed in the store, are you? Because I'll have to ban you if I find out you are", he assured me he was not. I watched him walk out, cross the street, and hand the bag to a recently banned customer. Mark was no longer allowed in the store.
I rarely saw Mark after that. Maybe twice, walking around the block looking for cigarettes.
I found out 2 days ago that Mark jumped off of an overpass into the highway. I feel partially at fault for cutting him off and not letting him have access to that vice, but that feeling is fleeting, as I cannot be responsible for that kind of self destruction.
It's okay Mark, we all could be/have been somebody, but it's rare that any of us ever are, at least in the way you thought it was to be "somebody". I hope you're at peace now.