Discipline was key to the Islanders wins in Games 1 and 4 and was a focal point entering the series, but down 3-0 in the second period, frustrations got the better of the team.
The Isles took four-straight penalties in the second period, allowing two power-play goals in the process to deepen an already deep hole.
Stamkos' second goal came at the tail end of Tampa's first power play, as the Bolts captain beat Ilya Sorokin with a one-timer from the left dot. Killorn's second goal also came via the power play, as he deflected a Hedman point shot past Sorokin at 17:53 to make it 6-0. The pair of power-play goals sandwiched Ondrej Palat's 5-0 marker, as the Bolts winger tipped a Savard wrister at 15:43.
"We got a little frustrated, that's what happens," Greene said. "At that point we just got to make sure we're trying to find our game there an build something there."
Matt Martin's fight with Luke Schenn didn't alleviate the tension, with a flashpoint coming at the end of the second period. Mathew Barzal was given a five-minute major and game misconduct for cross-checking Jan Rutta up high, which led to JG Pageau and Anthony Cirelli taking offsetting roughing minors.
Point put an exclamation mark on the Lightning's power play, scoring his playoff-leading 13th goal of the season during Barzal's major. Tampa's power play finished the night 3-for-6.
The rough stuff continued late in the third period, with Barclay Goodrow cross-checking Casey Cizikas, setting off a few more scrums and misconducts as the dislike between the teams deepened. In total, the Islanders finished the game with 57 PIMs to 28 for the Lightning.
"You're not going to win any games when you give up three power-play goals," Trotz said. "It took all the rhythm out of our bench. We were battling through it all night."