While roller skating.....
Depends on what said murderous killers want and whether or not you can disarm them or neutralize them without a fight.
Why kill when you can talk? Why talk to the N. Koreans when you can have the Chinese rein them in for us?
Continue negotiation, allow the South Koreans to continue detante', bribe the Chinese with some trade bonuses to reign in the North Koreans.
It's not quick, but nobody dies.