The Chiefs built a 3-1 lead in the first period with goals from Kasey Beirnes, Johnny Powless and Craig Point. Ben McCullough had an unassisted goal for the Shamrocks.
Point's second goal of the game gave Six Nations a 4-1 lead in the second period, before Rhys Duch cut the margin.
King got Victoria to within a goal at 5:39 of the third period, and he tied the game a little over minute later, before scoring the winner at 9:55.
Matt Vinc made 26 saves for the Shamrocks, while Evan Kirk made 39 stops for Six Nations.