It’s possible it was a prank, but if it was loaded before the shooting I really doubt it. Loughner put up a lot of nutty videos as well.
I suppose *maybe* he’s an operative of some group that’s trying to make right wingers look bad, but again that’s an awfully big assumption to leap to.
I could take my page today, delete most of the posts and friends, change out some information and update my name and photos with his info and make it look like he had the page for over 5 years. All the posts I made everywhere will show the new name and if it is done right (something a 10 year old could do) no one would ever know it was a different profile before.
Try it yourself if you have a Facebook profile. Keep it simple, just change the spelling of your last name, save it, clear your cache and history then go look at all the posts you made. It will have the new spelling. Same idea to completely change a profile name. Elementary prankster stuff.