A grand slam often ends up over a fence.

Greg Deichmann’s ended up under a bench.

The sophomore’s bases-loaded smashing shot bounded underneath LSU’s bullpen bench in a wild, first-inning grand slam that gave the Tigers a 4-0 lead over Rice on Sunday evening in the NCAA Baton Rouge regional winners bracket final.

Deichmann’s crowd-rousing screamer cleared the bases. He raced home after Rice right fielder Charlie Warren attempted to retrieve the ball, unsuccessfully, from under the bench. Umpires first ruled Deichmann’s shot a two-run, ground-rule double. After a brief huddle, home play umpire Scott Kennedy signaled the home run call, and a packed Alex Box Stadium roared in celebration for a rare inside-the-park grand slam.

“Threw a cureveball and saw it pop up out of his hand and I turned on it down the line,” Deichmann said. “I saw the first baseman’s mitt go up. As soon as it bounced, I was digging for a double. I saw it heading for the tarp. I picked up (third base coach) Nolan (Cain), and he was waving me all the way.”

It’s not the first of its kind in a regional at this stadium.

Then-LSU first baseman Tyler Moore hit a two-run inside-the-park home run against Houston in the NCAA Baton Rouge regional in 2014. His scorching shot — also down the right field line and also against a Houston-based squad — was pinned between the ground and the outfield gate at the right field corner. That inside-the-parker gave LSU a 3-0 lead over Houston in a game it eventually lost 5-4.

Deichmann’s shot put the Tigers up 4-0 in the first. He took Rice starter John Duplantier’s 26th pitch past first baseman Tristan Gray. The ball hit a couple of feet into fair territory before rolling under the wooden bench. Warren knelt down before rising back up and throwing up his hands.

What he did next cost his team. The sophomore knelt to the ground again and reached under the bench — an attempt at retrieving the ball.

“If the ball goes under the bullpen bench and remains under the bench, the ball is dead,” reads LSU’s ground rules, “… unless the defensive player goes in to retrieve it.”

Warren’s attempt to get the ball resulted in Deichmann’s unusual grand slam, the ninth homer of the season for the former Brother Martin standout.

Rice coach Wayne Graham said the ball was “lodged” under the bullpen bench, but the coach says he agreed and understood the ruling.

“The rules are very clearly stated — if you go for the ball it becomes live,” Mainieri said in the postgame news conference.

It was a wild scene.

As the ball rolled under the bench, Antoine Duplantis, Kramer Robertson and Bryce Jordan — all of them walked — raced around the bases. When Warren reached for the ball, Mainieri, watching the drama unfold, ran out of the dugout and signaled for Deichmann to keep running. The 10th-year coach frantically waved his arms into the air, and the Box thundered to life.

First base umpire Harry Greer then signaled a ground-rule double before Mainieri chased down the umpires, barking at three of them. A huddle ensued, and Deichmann had his odd grand slam.

“He held up his hands and that would have been fine, but then he started digging for it and you can’t do that,” Graham said. “Once you hold up your hands, the umpire has to go in there and see if it was lodged.”

Umpires then explained the play to Rice coach Wayne Graham.

“When it went under the bench and I saw the kid hold his hands up, I was a little discouraged. We were going to be at second and third (in a ground rule double),” Mainieri said. “Then the kid clearly started digging for it. I know what the rules are. Good umpiring. They all got together and talked about it. I’m sure the other umpires reminded the umpire at first about the rule.”