Boston goaltender Jeremy Swayman looks back at the puck as it crosses the line for a goal by Ottawa’s Josh Norris during the second period Thursday in Boston. Charles Krupa/Associated Press

BOSTON — Brady Tkachuk, Josh Norris and Tim Stützle each scored a goal in the second period and the Ottawa Senators beat Boston 3-2 on Thursday night, sending the Bruins to their first three-game losing streak this season.

Jesper Froden scored his first NHL goal for Boston and Marc McLaughlin added his third, just six games into his NHL career. The Bruins had won eight of 10 before the skid.

Long since eliminated from playoff contention, the Senators wiped out a 2-0 deficit with three second-period goals for their second consecutive win. Anton Forsberg stopped 40 shots for the Senators.

Boston’s Jeremy Swayman allowed a goal on the first shot he faced and finished with 21 saves after starter Linus Ullmark left following one period because of an undisclosed injury.

Swayman stopped two clean breakaways – both against Connor Brown – in the final period.

Ullmark took a slap shot off the mask early in the game from Erik Brannstrom and appeared to stumble a bit after the puck caromed away. He stopped all eight shots he faced.

The Senators scored their goals in just under 10 minutes in the second period. With Ottawa trailing 2-0, Tkachuk cut the deficit in half 47 seconds into the period by caroming the puck off Swayman on a shot from behind the net. The Senators then scored twice on the power play just 57 seconds apart.

Skating with a two-man advantage, Norris one-timed a shot past Swayman from the right circle.

Stützle then scored on a rebound, moving Ottawa ahead at 10:27.

Rookies McLaughlin and Froden gave Boston a 2-0 edge after one period.