David Pastrnak had a goal and an assist, and Charlie McAvoy had three assists for Boston, which is the No. 3 seed in the MassMutual East Division and has won three straight. Tuukka Rask made 19 saves for his 54th NHL postseason victory, passing Gerry Cheevers for the most in Bruins history.
"We wanted it and it showed," Bruins coach Bruce Cassidy said. "It showed out there. We've talked about getting better all the time as we go along, and that includes this series, that includes period to period. … I think we've progressively built our game here at home."
Ilya Samsonov made 33 saves for Washington, the No. 2 seed, which was 2-for-5 on the penalty kill.
"Yeah … they scored power-play goals tonight. And so, even though it went back-and-forth with the penalties, discipline still always factors into it," Capitals coach Peter Laviolette said. "Some of the penalties I don't like, some of them are part of the game. It's physical out there. At the end of the day, there's got to be discipline."