BOSTON — Anthony Beauvillier scored 21 seconds into overtime and the Islanders rallied from a two-goal deficit to beat the Bruins 4-3 on Thursday night in the first major league sporting event in Boston with fans in attendance since the pandemic shutdown.

The Islanders trailed 2-0 after one period but Jean-Gabriel Pageau cut the margin in half in the second, Josh Bailey tied it in the third and Oliver Wahlstrom gave the Islanders the lead with 2:56 left in regulation. Just 54 seconds later, though, Anders Bjork tied it again.

Right after the faceoff to begin the extra period, Nick Leddy brought the puck into the Boston zone and snapped off a shot that bounced off goalie Jaroslav Halak and trickled into the crease. Beauvillier came along to swipe it in.

“We got the two points,” Islanders coach Barry Trotz said. “That’s all we care about, collecting points.”

Semyon Varlamov stopped 25 shots for the Islanders, who won their third straight and 12th in the last 14 games.

Karson Kuhlman and Steven Kampfer scored for Boston, and Halak stopped 14 of the 18 shots he faced after relieving Tuukka Rask to start the second period. Rask, who hadn’t played since March 7, left with an unspecified injury.

A mostly masked crowd of 2,191 — 12 percent of capacity — was at TD Garden to see the Bruins return from a weeklong pause after five players went into the NHL’s COVID-19 protocol. (Two games were postponed.) They cheered heartily when Boston opened a 2-0 lead in the first period; other times, individual shouts could be singled out in the building, which usually holds 17,850 for hockey.

“It’s not going to replace 18,000. But it’s nice to hear them again,” Bruins coach Bruce Cassidy said. “Unfortunately, we couldn’t send them home in a better mood. I’m sure they’re frustrated, but we are as well.”