Thursday night saw the loudest of bing bongs.

The New York Knicks erased what was once a 25-point deficit against the Boston Celtics, but it was only once the game was tied with two seconds left that things went truly off the rails.

Following a clutch fadeaway by Jayson Tatum to tie the game, the Knicks inbounded the ball to RJ Barrett and watched him make a preposterous, off-balance, buzzer-beating 3-pointer to blow the roof off Madison Square Garden.

Entering the game, the Knicks were 1-229 when trailing by 25 points or more in a game in the last 25 seasons, with their only win coming in 2004, per ESPN Stats & Info.

Barrett was the hero of the moment, but the overall hero of the night was Evan Fournier, who joined the Knicks this season after finishing last season with the Celtics. Facing his old team, the Frenchman went off for a career-high 41 points on 15-of-25 shooting (10-of-14 from 3-point range, tying a Knicks team record) plus eight rebounds.

Torching the Celtics has been something of a theme for Fournier this season, as he had previously scored 32 points in each of his two other games against the team. He has not scored north of 30 points in any other game this season.

Celtics coach Ime Udoka says team lacks mental toughness

For that and many other reasons, Thursday night figures to haunt the Celtics. The team held a 57-32 lead with less than four minutes remaining in the first half, but allowed the Knicks to carve out the faintest of hopes by reducing the deficit to 16 points at halftime.

The Celtics held on for a while in the third quarter, but their lead was down to single digits with a few minutes left. One last push in the fourth put New York in position for a shocker.

It was the kind of performance that had their coach openly questioning their mental toughness after the game:

As usual, Tatum carried the offense with 36 points on 12-of-21 shooting but beyond him and Dennis Schroder, the team shot 38.3% from the field.