Boston Bruins’ Zdeno Chara, left, reaches behind goaltender Tuukka Rask to keep the puck from crossing the goal line during the second period in Game 7 of the Stanley Cup Final against the St. Louis Blues on Wednesday, June 12, 2019, in Boston. (Bruce Bennett/Pool via AP)

BOSTON — The Boston Bruins will look back on three minutes all summer.

The Bruins had it all lined up: a raucous home crowd for its first Game 7 of a Stanley Cup Final in their 95-year history, was aided by a couple of world champions from other sports and a fast start that provided a handful of excellent scoring chances in the opening period.

Then in a matter of three minutes because of a slow line change and a bad turnover by forward David Pastrnak, it was gone.

The St. Louis Blues stunned the Bruins and their fans with two quick goals, took that 2-0 lead into the first intermission and cruised to a 4-1 win Wednesday night to celebrate their first championship.

Also gone was the city’s chance for its 13th championship since 2002 that would have joined the New England Patriots’ six, four by the Red Sox and one each by the Celtics and Bruins.

After Patriots Super Bowl MVP Julian Edelman and Olympic champion gymnast Aly Raisman — both wearing David Ortiz white home jerseys as the honorary flag bearers — came out and fired up the crowd Boston came charging out quickly before its momentum disappeared late in the opening period even quicker.

They even showed 2004 World Series star Curt Schilling on the Jumbotron flashing his championship ring. Boston was searching for its first Cup since 2011 when it beat Game 7 in Vancouver, but nothing worked.

The Bruins were handed a power play on a delay of game penalty by Blues defenseman Colton Parayko 7:57 into the period and they certainly had their chances — like they did for a lot of the opening 10 minutes of the game.

Brad Marchand, the team’s leading scorer in the postseason, was robbed by Jordan Binnington on a wrister from the slot. After the penalty was over, David Krejci cut in alone and Binnington flashed his right pad to rob his backhander from the edge of the crease. They had another excellent chance when Marcus Johansson came charging in alone from the right circle, but Binnington dove out to make the stop.

That’s when Boston seemed to fall apart defensively late in the period. On slow change, the Blues collected the puck in the neutral zone and defenseman Jay Bouwmeester fired a shot from the point that Ryan O’Reilly tipped between Rask’s pads at 16:47.

In the closing seconds, Pastrnak gave the puck up in his own end. Jaden Schwartz sent a pass to Alex Pietrangelo and the defenseman beat Rask with a backhander to the blocker side from the slot with eight seconds left.

It was the Blues’ night from then on. Tuukka Rask had stopped 82 of 86 shots in Boston’s three elimination games this season (twice in the opening round against Toronto and Game 6 in St. Louis) but the Blues got to him early and made it stand up.