Well, it happened folks. The Boston Bruins choked away a 3-1 series lead against the Florida Panthers, losing 4-3 in overtime in Game 7 to send the best regular season team in NHL history spiraling into another offseason full of uncertainty. In the aftermath of their stunning loss, the Bruins and their fans are likely all thinking the same question; how did this happen?

The Bruins were a juggernaut throughout the regular season, and even early in the series, it looked like they had all the answers against the Panthers. But they slowly unraveled, passing up opportunity after opportunity to put Florida to rest, and it all ended up being too much to overcome after the Panthers managed to force overtime with just under a minute left in Game 7.

All these issues the Bruins were hoping they would be able to deal with after winning a championship now have to be dealt with far sooner than expected. But first, it's only right to dive back into the mess and figure out where things went wrong. So with that in mind, let's look at the three biggest reasons the Bruins completely fell apart against the Panthers in their first-round playoff series.

3. The Bruins struggled score in even-strength situations

It's strange how much the game of hockey changes once the playoffs roll around. Entering the postseason, the Bruins power play units had been struggling to consistently score goals, and it was viewed as maybe their one weakness. But by the time the series came to a close, Boston very nearly could not score when they were playing at even-strength against the Panthers.

Through this seven game series, the Bruins scored 27 goals, but of that tally, 12 of them came on the power play, and three more came off of shorthanded situations or were empty-netters. That means that Boston scored less than half of their goals in even-strength situations against Florida in this series. That's not exactly a winning recipe since hockey is played at 5-on-5 for the majority of its 60 minute runtime.

This is an issue that became more and more prevalent as the series went on, especially with the Bruins finding themselves playing from behind so frequently over their final three losses, but it's just as big of a problem as the two other issues we will look at in a second. The Bruins were the most dominant even-strength team in the league in the regular season, but they tightened up to the point where they simply could not score during 5-on-5 play against the Panthers in this series.

2. The Bruins received poor goaltending throughout the series

Boston's goalie duo throughout the regular season was arguably the best in the league. Linus Ullmark is almost certainly going to win the Vezina trophy as the league's best goaltender, and Jeremy Swayman was no slouch as his backup either, posting a save percentage of 92 percent and allowing just 2.27 goals per game.

Yet in the playoffs, that goalie rotation quickly turned into Ullmark running the show, and he wasn't particularly very good for the Bruins against the Panthers. Ullmark went from allowing 1.89 goals per game to 3.33 against Florida, and his outings in Games 5 & 6 were particularly awful. Swayman was thrown into a tough situation starting Game 7, and while he made some big saves, he still allowed four goals himself.

You can't totally fault Swayman, who held his own amid awful circumstances, and Ullmark, who was almost certainly playing with some sort of injury, but Boston's goalies bailed them out time and again during the regular season. That just didn't happen in this series, though, and had one of these guys managed to step up at any point in Games 5-7, maybe the Bruins would be advancing to the second-round.

1. The Bruins carelessness with the puck consistently led to goals for the Panthers

Easily the biggest reason the Bruins lost this series was due to their desire to just give the Panthers the puck. Boston finished this series with a whooping 88 giveaways in seven games, with the Panthers constantly turning those plays into goals. It was stunning to see the Bruins just keep losing the puck, whether it was a wayward pass or the Panthers just wanting it more than them.

Part of the reason you can't harp too much on the goalies is because they kept getting put into situations where they couldn't win. You'd like Swayman to save the game-tying and game-winning goals in Game 7, but the defense is hanging him out to dry. Montour was unmarked right in front of Swayman on his late third-period goal, while Matthew Tkachuk just outwilled two Bruins defenders to free the puck to Carter Verhaeghe for the game-winner. Again, it all loops back to Boston not being careful with the puck.

Maybe it was the nerves or the pressure that got to the Bruins, but this is a veteran-filled team that has been in pretty much every playoff situation possible. Every season since their 2011 Stanley Cup victory, Boston manages to find a way to trip themselves up, and in what may be their last chance to win with Patrice Bergeron and David Krejci, they did it once again, setting the stage for what could be a demoralizing offseason.