Steering issue 03 6.0

[mikeb01453]

Ok so here is the deal, I was driving down the load doing maybe thirty and began braking to take a right turn, I hit a small bump and heard a loud snap which I concluded was my rear leaf spring snapping ( it is broken this I know for a fact) but the other issue is I just had four tires put on and a front end alignment but within a few minutes I started to notice my truck no longer steers straight on it's own. My steering wheel was perfect before but now I have to have the wheel at five o'clock to get the truck to steer straight but I can't see anything it all broken other then the rear leaf spring. Anyone have any idea what the issue could be, I'm kinda leaning towards the bolts for the alignment not being tightened but I can neither confirm nor deny this possibility. Just wonder what I should be lookin for. Thanks alot guys