The End Was totally unrealistic-SPOILERS
I liked the movie so I'm not complaining but it did get pretty unrealistic at the end when they tried to murder Tom and Maggie. The death of the dead girl was more a freak accident so it doesn't make any sense because the two sons would probably get something like 10-15 years and be free after maybe 5-10 years(ok, I'm not a law expert). If they would kill the couple in cold blood, they would get several life sentences on top.
Since the murder attempt is done in such a sloppy way, there is no doubt that they would get caught. I'm not sure if that ending was even necessary.