Are those the only items that were taken?
Important question because generally if you're robbed and the only thing missing is say, your hidden stack of cash, then it had to be someone who knew about it.
Thieves who don't know where, or what to look for, take everything they can and often make a mess. There is the possibility that criminals can stage a crime scene to make it look like a ransack when in fact all they wanted was "X" item, but that will take a savvy detective to figure out.
That said, it sounds like it was some "friends." I'd keep a close ear to the ground. Maybe set 'em up too. Talk loud about some new guns you just bought and stage a camera by an outdoor shed.
avid crime show watcher
edit: They left the broken pistol? That's an important clue. Why did they leave it? Did they already know it was broken and not worth taking? Who knew it was broken?
Also the pants is interesting but it might not be important. It could be the perp didn't take them because they didn't fit, which would give you some bracket of size to work with. However, it could be they just didn't like the pattern...but that seems rather "picky" for a thief who's stealing because he's hungry or having withdraws.