Catching a 300-pound killer shark is supposed to be a once-in-a-lifetime event.

But nearly three years after commercial fisherman John “Willy” Dean hauled in the first bull shark recorded in the Potomac in 37 years, he repeated the feat Tuesday — twice.

The first of the two bull sharks Dean caught Tuesday in the waters off of Point Lookout State Park at the tip of St. Mary’s County was already dead in the water. Sharks need a constant flow of moving water to breathe, Dean’s son Greg said. Constrained in a net that the Deans use to take in fish every day, the shark drowned before they pulled it aboard.

Still, the shark — more than eight feet long and one of the deadliest fish for humans — was imposing.

“It was a good adrenaline rush, I would say,” Greg Dean said of the first shark. “It was a little scary, but then at the same time, it was very exciting. We really just don’t think at that point. We just keep pulling it in and try to see what it was.”

A Maryland Department of Natural Resources biologist happened to be aboard for a routine check, reported, and the scientist immediately identified the massive creature as a bull shark, a species that can tolerate fresh water.

Greg Dean and the biologist returned to shore with the shark, and Willy Dean and deckhand Patrick Ridgell went back out to collect their ordinary daily catch. They saw fish acting strange, maybe even frightened, swimming closer to shore than usual. Then Willy Dean and Ridgell saw something that looked like “a big gray cloud,” as Greg Dean put it. And then a dorsal fin.

They called Greg Dean and a second deckhand, Richard Richie, who met them in the water. All four men hauled in the shark caught in the net this time — and this one was alive.

“Pulling it in the boat was very hard, but once we did that, we just kept a safe distance,” Greg Dean said. When you’re on a boat with a thrashing eight-foot-long shark, though, a “safe distance” means only a few inches. Luckily, a shark out of water has little ability to move forward.

“He can still snap his jaws, which he was still doing. We saw all those rows of teeth he had that were razor sharp,” Greg Dean said. “This is one of the most deadliest creatures on Earth, and we had him just a few inches away from us.” Minutes later, the shark was dead.

When they returned to shore, the Deans put both sharks in a walk-in storage area so curious neighbors could see them. Greg Dean said they plan to donate at least one of the two carcasses to scientists for research, but they may cut one up for shark steaks.

While the second shark was in the net, Greg Dean watched it swallowing foot-long fish whole.

“It’s very scary to think that that could be honestly someone’s arm,” he said. “That could be your foot.”

He advises swimmers not to venture into that part of the Potomac at night. As for why the sharks have been spotted there in two of the past four Augusts, Greg Dean says it is anybody’s guess.

“I look at it like this. They’ve been out there for a very, very long time. And I guess a lot of them are figuring out when the water gets a little bit warmer, they can go a lot closer to the shore to get their food instead of being way out in the deep,” he said. “Everybody has their theories. That’s mine.”