After a scoreless first period, Östlund recorded his first point when he set up teammate Bowen Byram to equalize eleven minutes into the second period.
Then Boston's Viktor Arvidsson missed a penalty just a minute earlier.
Before the game was over, Östlund scored the decisive goal with a wrist shot with 1:24 left in the third.
With the victory, Buffalo, playing in the playoffs for the first time in 15 years, takes a 2–1 lead in the series.
Corrected version: In a previous version, the wrong surname was given for Viktor Arvidsson.
Round of 16:
Buffalo–Boston 3–1 (Buffalo leads 2–1 in games)
Carolina–Ottawa 2–1 (Carolina leads 3–0)
Los Angeles–Colorado 2–4 (Colorado leads 3–0)
