The Ending (SPOILER)

MF Jones kept the money and bought the business (cupcakes?) he talked about wanting earlier on.
Spacey's character bought the guy's business when it folded and kept the 3 on as his workers which is why they report to him at the end.
So the irony being, they now all have a horrible boss again lol

Ok here's the whole ending:

It's revealed that Rex Hanson (Chris Pine) is the REAL horrible boss/psychopath as he murders his father and let's the trio take the fall. However, just when before the police come MF Jones comes in to rescue them/take the ransom.

They realise that Rex is going back to the warehouse to prove he was kidnapped, but so the trio and Jones drive as fast as possible to get to the warehouse. However during the way, he notices them being tagged by the police, so he outsmarts them, still getting the trio to take the fall.

But then, Dale remembers he has the dagger thing from the Preadator film that Rex gave him, so he attempts to stab him only to get shot by him. Then the police start tackling Rex, and Detective Hatch is looking after Dale.

Two days later, Nick and Kurt visit Dale in the hospital, telling him everything that has happened ever since he got shot.

P.S I wonder what happened to Rex, I know he's most likely in prison but it seems to me he might appear in HB3? (Horrible Bosses 3)