why were the 2 guys chasing the old guy?

The "two guys" are the stepsons of the "old guy" the mother/wife knew he was cheating and wanted them to do something about it. I think they thought they were just going to scare him - not give him a heart attack and kill him

I thought it was pretty obvious as to why they were chasing him... However, a lot of folks felt this movie sucked, so I guess they couldn't bare to watch the first 10 minutes which reveals why...

The brave may not live forever, but the cautious do not live at all.