Subject: Re: Did the rifle have a scope?
Since he didn't leave the weapon on the rooftop, he must have disassembled it and put it in his backpack.

Nah. Nobody’s going to take the time to disassemble it; you’re going to run like hell to get out of Dodge.

Probably he just threw it off the roof and picked it up on his way to the woods. That also answers the “he reassembled it later” thing.

I can’t figure out why he would leave it in the woods for others to find later. There has to be DNA on it, maybe it’s registered, maybe somebody else has seen him with it in the past. Obviously he doesn’t watch enough episodes of Forensic Files to be educated in the many and various ways the police have of finding you - and bragging about it, well that’s just the stupidest.