I think Adam would still be capable of anything, anytime. Just because some say he might have been reformed by fatherhood and/or true love doesn't mean he wouldn't do worse than he'd ever done before if, in his mind, he was protecting his son. And more important, regardless of whether or not he's reformed now, it doesn't means he's forgotten HOW to do all those things.
OK; maybe he didn't need to kill anyone. Suppose he had a "Go-kit" on hand in his car with a change of clothes, ID, cash, etc. After Billy got away, Adam gets the kit, dons his disguise, throws the clothes he was wearing, along with his ID and jewelry, into the car and pulls the wires. After the BOOM the hapless GCPD takes a while to sift through the rubble. They may not find any actual human remains, but by the time they know what they're dealing with, Adam could be in Timbuktu. That's a good head start.
I still say: WAIT - if we never hear Paul and/or Nick wonder where the guy in the woods might be or if they know where he is, then please forgive my irrational ravings. However, the minute one of them wonders what happened to the guy, we're off to the races. After all, why wouldn't an honest-to-goodness Good Samaritan stick around?