Georgetown Prep topped Bullis, 11-10, after scoring six straight goals in the fourth quarter. (David J. Kim/For The Washington Post)

After Zach Whittier fired a shot from the right side with 1:42 left in Tuesday’s game, he tumbled and rolled on the ground. He didn’t get a clear view of the ball blazing past the opposing goalie to give his Georgetown Prep lacrosse squad the lead, but as soon as it found the net, the players on the field mobbed the sophomore attacker and those on the sideline celebrated in unison.

Whittier realized then that his shot had gone in.

His goal capped a dramatic comeback for the No. 3 Little Hoyas, who erased a five-goal fourth-quarter deficit to earn an 11-10 win at No. 2 Bullis in Potomac to clinch the Interstate Athletic Conference regular season title.

“When we had the ball on offense, we weren’t trying to rush. We were just calmly running our offense,” said Whittier, who scored three goals. “The last goal, I just went top side, went low and buried it. Just dunked it.”

The two rivals, undefeated in conference play heading into this regular season finale, are considered two of the best in the region and they played like it. From the onset, Georgetown Prep (14-3, 5-0 IAC) relied on its defense, which has allowed just two opponents to score in double digits this season. Anchored by seniors Clay Lanham and Jake Giulieri, the stingy defense held steadfast against the high-scoring Bullis offense until the third quarter.

The Bulldogs (17-3, 4-1) eventually took advantage of Little Hoyas unforced turnovers and penalties. Sophomore Connor Davis scored two goals in two minutes to give Bullis its first lead with 7:15 left in the third. Senior Robert Schain’s fadeaway jump goal with 2.8 seconds left in the quarter gave Bullis a 10-5 lead.

“When we got down five goals, no one started hanging their heads,” Lanham said. “Once we dug down in that hole, we all started remembering the last three seasons here. They ended our seasons here, and we weren’t going to let that happen today.”

Prep hadn’t beaten Bullis since 2015, and the Little Hoyas showed urgency in the fourth quarter to begin spoiling Bullis’s senior night. Lanham started the final quarter with a transition goal, sprinting more than 40 yards on the play.

Feeding off the energy, seniors James Flannery and Connor Humiston each scored a goal. By then, the momentum had shifted.

After two more goals tied the score, Whitter’s final shot in the extra-man offense finished the comeback win.

Both teams will receive a first-round bye in the IAC tournament, which begins Friday.

“From here on out, it’s sudden death,” Lanham said. “I want to take this season as long as I can with this group of guys and get a championship we can share together forever.”