Joe Pavelski got the scoring started 42 seconds into the game for the Sharks and had two assists. Melker Karlsson had a goal and an assist, also in the big second period when the Sharks capitalized on a string of Bruin penalties.
Brad Marchand, Loui Eriksson, Patrice Bergeron and Tyler Randell each scored for Boston. The Bruins pulled within 5-4 on Bergeron's power-play goal at 13:32 of left to play but could not overcome their second-period mistakes.
Eriksson's goal 1:53 into the second put Boston up 3-2, the last lead the Bruins would hold. Karlsson tied it with a goal 5:56 into the period, then the Bruins committed four straight penalties and San Jose capitalized with power-play goals by Marleau and Thornton.
Boston was called for too many men on the ice late in a power play and San Jose took a 4-3 lead when Marleau scored on a rebound 8:56 into the second period. Boston coach Claude Julien challenged the call, saying Thornton interfered with Rask as Marleau got the puck behind him, but the goal was upheld.
Boston was at even strength for all of 11 seconds before Ryan Spooner was called for interference. The Sharks pounced quickly and took a 5-3 lead on Thornton's one-timer from the slot at 9:21.
Notes: Seidenberg played in his 700th game. Boston D Adam McQuaid played in his 300th game. ... Thornton, the former Bruins' captain, has four goals and eight four assists in 12 games against Boston. ... The Bruins have yet to win consecutive home games this season.