MARYVILLE, Mo. — A Kevin Buckingham three at the buzzer in regulation sent seventh-seeded Southeastern Oklahoma State to overtime on the way to a 115-103 upset of second-seed Northern State in the quarterfinals of the NCAA Division II Central Regional on Saturday.

The Savage Storm (23-7) advances them to the region semifinals and will face No. 6 seed Missouri Southern State which upset third-seeded Washburn, 101-100, in the tournament’s opening game, at 5 p.m. on Sunday for a spot in the Sweet 16.

“I’m 56 years old and I’ve been doing this since I was like 22,” Southeastern head coach Kelly Green said. “I have never seen anything like that in my life. We couldn’t stop them. They just kept hitting shot after shot. It’s funny, we knew we had to get over 80 or hold them under 80 to have a chance but we just couldn’t stop them. Everybody kept hitting threes and a couple of our guys didn’t have their best games.

“I go back and I watch film after wins and losses to figure out what happened,” he continued. “I’ve got no idea what happened, he [pointing at Buckingham] just started making shots. We played an outstanding team. They are so difficult to guard, they’re physical and they run their stuff so well.”

Southeastern stared down a 13-point deficit at 83-70 with 2:12 to play in regulation when Adam Dworsky connected on a jumper to kick off a 10-0 run that closed the gap to 83-80 with 1:26 remaining.

NSU answered that run with a bucket but a Kayo Goncalves three closed the gap to 85-83 with 1:02 left in regulation.

The Wolves followed with a three and added a free throw with 21 seconds to go before Buckingham connected on a three with 17 ticks remaining and ultimately his game-tying three at the buzzer to send the game to overtime tied at 89.

The Storm scored first in OT on a Jett Jobe layup and opened the frame on a 7-1 run to take a 96-90 lead at the 3:28 mark.

NSU answered with a three to cut the deficit in half but the Storm responded with an 8-0 run on a pair of Dworsky buckets and a 4-for-4 effort at the free throw line by Buckingham to go up 104-93.

A 6-1 Wolves run closed the advantage to six points with a minute to play but that was as close as it got the rest of the frame.

Buckingham posted a career-high 43 points, hitting 15-of-20 shots from the field and going 5-of-6 from beyond the arc to.

Dworsky added a career-high of his own, dropping 32 points on 13-of-19 shooting with a pair of threes.

Kellen Manek finished the game with 15 points while Jobe added 12 points and Goncalves chipped in eight points off the bench.

Southeastern shot 58.1 percent from the field and 47.8 percent from beyond the arc, draining 11-of-23 threes.

Dworsky just missed a double-double with nine assists as the Storm finished with 16 as a team.

Buckingham and Manek each finished just short of a double-double as well as each hauled in nine rebounds.

Both teams came out trading punches with four ties and four lead changes over the first five minutes before NSU pulled out to a 16-11 lead at the 13:23 mark.

A 10-3 Southeastern run erased that gap and the Storm took a 21-19 advantage on a Manek bucket with 11:09 to go in the half.

The Wolves regained the lead but Southeastern recovered to tie the game at 27 on a Dworsky layup with 7:25 to go.

NSU followed with 11 straight points and outscored the Storm, 21-8, over the final seven minutes for a 48-35 half-time lead.

That was as wide as the margin would get as Southeastern chipped away at the deficit early in the second half, getting it to single digits four times before a run pushed the deficit back to 13 points with 9:13 to play in regulation.

A 7-0 run powered by Dworsky and Buckingham got the Storm moving and a Buckingham layup at the 5:39 mark closed the gap to 73-68 with 5:39 to go.

However, another NSU run stretched the deficit back to 13 points with 2:12 to play, setting up the late game heroics.

Buckingham accounted for 14 points over the final two minutes of regulation.

Dworsky finish the OT period with nine points while Buckingham added eight as the Storm tallied 26 points in OT alone, the highest overtime output since matching the NCAA DII record for points in an OT session with 28 against Harding during the 2016-17 season.