Theres some sort of fouled anchor emblem on the chain around his neck. The chain's heavier than a military dogtag chain, but I'd bet that the fella has been out of the Navy for quite sometime, based on his weight.
The body armor report sort of explains why the cops left him with his shirt pulled open. Looks like the buttons are still in place, but it may be a bit difficult for him to fasten them with his hands in back.
I understand he was a former fishing boat captain.