Bottom line - Don't mess with a mom!
F'ing great that they turned the tide of this battle. I'm sorry they had to kill the guy, only because though they had every right to and I would have done the exact same thing, I expect that it will haunt them for a while. I couldn't care less that this one douche bag is dead, I just hope their family recovers OK from it.
These thugs were probably expecting to dominate the scene since they had guns. The moment these people showed they were not afraid, the bad guys got scared. Nothing but two bullies...one bully now
Never give up, never surrender.