Hats rained down on the TD Garden ice for Pastrnak, and for the first time in a long time, there was a postseason buzz that reverberated throughout the arena with fans standing, cheering and chanting in bunches.
"It was just a nice moment to look around. Enjoy it. It's playoff hockey. That's what it's all about," Bruins coach Bruce Cassidy said. "I'm sure we'll feel that in New York, too, when we get there. But it was our turn to sort of take it all in here. So, that's what I did."
It helps when you have Pastrnak on your side, as well.
"It's a different sport with them in the building. It warms your heart and reminds you why you play the sport," Pastrnak said. "You could tell, right from the warm-ups, the fans were going to help us."
Charlie McAvoy and Taylor Hall also scored, and Patrice Bergeron had a pair of assists for the Bruins, who will host Game 2 on Monday night.
Tuukka Rask finished with 20 saves as the Bruins kept most of the action at the other end of the ice, outshooting the Islanders 40-22.
Rask didn't allow anything past him after Adam Pelech's goal for the Islanders 12:34 into the second period tied it at 2. It was one of only four shots in the period for the Islanders.
"There were a lot of good things tonight on our assignments," Cassidy said. "It was a crisp game, and we managed the puck."
McAvoy concurred, and he believed it started up front.
"Our forwards played great tonight. They had great pace," he said. "Lots of great chances and lots of great looks. When we do that, with our offense, often times we are able to carry the momentum of the game."
Anthony Beauvillier also scored for the Islanders, Jordan Eberle had two assists and Ilya Sorokin finished with 35 saves, keeping New York in it through the first 40 minutes despite the onslaught of shots from the Bruins.
Sorokin stopped Pastrnak twice on one-timers from in close in the first period, but couldn't hold off the Bruins sharpshooter as he got his second career playoff hat trick.
Pastrnak, whose first postseason hat trick came three years ago in Game 2 of the opening round against Toronto, scored his third Saturday after weaving through the Islanders' zone and ripping a wrist shot past Sorokin 14:10 into the third period.
The hats began flying from all levels of the arena, which got loud enough to shake over the few minutes it took to clear the ice as elated Boston fans celebrated being back inside the arena and an imminent victory by the Bruins.
Pastrnak's goal and an empty-netter by Hall in the final minute triggered several anti-New York chants and a few rounds of "We want the Cup!"
"Obviously, Pasta is a goal scorer," Cassidy said. "He's found his touch."
The Associated Press contributed to this report.
Pastrnak's hat trick gives Bruins Game 1 win over Islanders
David Pastrnak scores a trio of goals to lead the Bruins past the Islanders in Game 1.