Yeah, I feel badly for the store clerk.
So I am thinking a bit more about how he is dressed.
If cvaldez1975 and the first released reports are correct and this man is closer to 40 I'll throw out some things that struck me.
These are just some general impressions (which are likely to be clouded by my own cultural/social experiences)
1. The chain- not that it matters (since it's not going to help identify him) but I'm wondering if the chain is a multi tool accessory, like for a leatherman. I used to have a short chain for mine so I wouldn't misplace it and didn't want it attached directly to my belt loops. Something like this swiss army knife chain:
http://www.adorama.com/vi33552.html?gclid=CIKIyoT44c0CFcokhgodsFIFMw
2. He could have purchased his clothes at a salvation army or similar, but my guess is he still considered what he was wearing carefully. Sort of a uniform rather than a disguise iykwim. His look reminds me a lot of how the late 80s/90s hardcore straight edge kids dressed. Part of that culture often included a transient lifestyle of traveling from show to show and crashing at different "punk houses" (kind of like a punk equivalent of a commune or group house-often these were shared industrial lofts where the shows themselves were held).
This is all a long shot based on a blurry video, but if he's ever travelled in any scene/punk/hardcore circles maybe someone from that seen will remember him.
3. The cap and possible bandana were two things that flag that subculture for me (although I guess it's possible that's not a bandana but the towel used in the crime? ugh.)
Here's a cartoon that turned up when I searched for straight edge hardcore fashion (not exactly what I am thinking of but close enough for an example) :
http://www.dobi.nu/yourscenesucks/