In a seesaw fourth quarter which featured six lead changes and two ties, Carson ended up making one more play than Spanish Springs.
With time winding down and the score knotted at 37, the Cougars' Kenny Meyer was pickpocketed by the Senators' Alan Cohen, who handed it to teammate Chris Lopez before dishing it up ahead to a racing Rafe King.
King went up for the game-winning layup before being fouled by Spanish Springs' Hunter Pinto as the buzzer sounded.
Once the referees concluded the foul occurred with 0.3 seconds remaining on the clock, King swished the first shot, sending Carson to the Division I North semifinals in a thrilling 38-37 win.
"I wasn't that nervous for the very first one because I had two shots," said King, who tallied a team-high 13 points. "They kind of iced me a little bit with all the timeouts and the refs talking, but when I got out there, I just knew I was going to hit the very first one."
The Senators trailed the entire game until taking their first lead with 5 minutes, 44 seconds remaining in the final quarter. Down by as many as 10 points, Carson never pushed the panic button.
"We've been in that situation before," Senators coach Carlos Mendeguia said. "Earlier in the season at Wooster, we were down 17 at the half. We had our backs against the wall and fought back to win that game by seven. All that prepared us for something like this where we didn't panic. ... We don't crack when we're down."
The heartbreaking loss had Spanish Springs coach Kyle Penney second-guessing his final play call that could've clinched a victory for the Cougars.
"We came out and wanted to get a quick ball screen and some penetration, and that's my fault," he said. "It's 100 percent my fault on that one. That's not the right play in that situation. That's on me."
The Senators return to their home court Thursday, welcoming McQueen in the semifinals. The two squads last met Dec. 18 in a 54-38 win for Carson.
However, the Lancers aren't exactly the same team. The presence of DaeShawn Patterson has ignited the red-hot Lancers, who are on a four-game winning streak.
"He's creating major problems for everybody," Mendeguia said. "He's a big 6-foot-7, 250-pound kid and he's very athletic. He's built confidence for that team."