Bemidji State, the fourth seed, stunned Wisconsin, the Big Ten regular-season champion and top seed in the East Regional, 6-3 on Friday in Bridgeport, Conn.
The Beavers (16-9-3) led 2-0 after the first period and 4-1 after the second. Cole Caufield, the nation's leading scorer, had two goals in the third period — his 29th and 30th of the season — to get the Badgers within 5-3 with just over five minutes to play.
Bemidji State was 0-6-1 vs. Wisconsin in the all-time series, but they had not met since 2011-12 when both were in the old WCHA.
Ross Armour gave coach Tom Serratore's team a 1-0 lead 6:33 into the game and Elias Rosen doubled the margin with an unassisted goal with 15 seconds left in the first.
Linus Weissbach of the Badgers (20-10-1) got the first goal of the middle period about four minutes into it, with Caufield getting one of the assists.
It stayed 2-1 for almost 11 minutes until Ethan Somoza got his 14th goal of the season for the Beavers at14:42 and then came the real backbreaker. Owen Sillinger scored an unassisted, shorthanded goal at 18:39 for a 4-1 lead into the third.
Somoza's second goal of the game about six minutes into the final period put the Beavers ahead 5-1.
Subsequently, Caufield tried to rally Wisconsin with his two goals but that only got them within two. Brendan Harris of the Beavers got a shorthanded empty-netter in the last seconds for their sixth goal.
Zach Driscoll made 30 saves for Bemidji State. Robbie Beydoun stopped 24 shots for the Badgers in the first two periods, Cameron Rowe 10 in the third.
This is Bemidji State's fifth trip to the NCAA tournament (2005, 2006, 2009, 2010). They were 2-4 in tournament play, including a 2009 trip to the Frozen Four.
The Beavers, who finished fourth in the WCHA this season, have won seven of their past nine games, outscoring their opponets 28-18 in that stretch.
Massachusetts 5, Lake Superior State 1: Jake Gaudet scored two goals — his team's first and fourth to lead the Minutemen (17-5-4) over the Lakers (19-7-3) — the second WCHA team in this regional. The first period ended tied at 1-all. Gaudet scored midway through the period but Ashton Calder got Lake Superior State's only goal seven minutes later.
Josh Lopina's goal at 11:03 of the second period proved to be the winner for UMass.
North Dakota 5, American International 1: The Fighting Hawks (22-5-1) took control of this game against the Yellow Jackets (15-4) at Scheels Arena in Fargo early, scoring four goals in the opening period. Jasper Weatherby had the first two, his 13th and 14th of the season, three minutes apart in the middle of the period. Grant Mismash and Collin Adams had other two goals, two minutes apart.
It stayed 4-0 until Tobias Fladeby's power-play goal for American International at 17:46 of the third. Adams got his second goal for UND 29 seconds later.
Adam Scheel mad 24 saves for North Dakota. Two Yellowjackets goalies combined to stop 28 shots.