Two boats moved slowly across the scum-covered water as a bank of TV cameras documented their every move and radio reporters did play-by-play. The poison rotenone, which smelled like mothballs, hung in the humid morning air and left visible trails in the water.
The torpedo-shaped fish from China made a beeline for shore, jumped in the air and even tried to hoist themselves onto lily pads to escape their fate. But in twos and threes and then in larger numbers, 3- and 4-inch baby snakeheads succumbed and bobbed to the surface.
"We're fairly confident that this rotenone is going to do the trick," said Schwaab. "But it may be several days before all the fish are dead."
Just in case, he added, the DNR's state permit allows for the application of a second dose of poison, which is absorbed through the gills and blocks a fish's ability to process oxygen.
The rotenone was applied two weeks after biologists sprayed an herbicide cocktail on the dense grass and lily pads to make it easier to reach the snakeheads. But their hope that the weed-killers might stress and kill some of the fish didn't pan out.
Steve Early, who managed the logistics of the spraying for the DNR, said the fish in the pond had adapted so well to low oxygen levels that they were able to survive the additional oxygen depletion caused by the vegetation kill.
Since the first one was caught and photographed 11 weeks ago, the snakeheads have become Maryland's most famous fish, generating tabloid headlines, TV comedy routines and competing T-shirt lines.
Yesterday was no different.
Customers at the Dunkin Donuts along Route 3 gawked at the row of TV trucks, and merchants shook their heads.
At the Family Bikes & Skates shop, manager Jonathan Seibold lamented the end of an international news story taking place outside his back door.
"I used to fish in that pond when I was a kid," he said. "And here it is, international news, I'm seeing it happen and I'm in it. ... It's been pretty hysterical."
Scientists recommended eradicating the snakeheads, out of concern that the versatile fish - which can survive out of water for up to three days and even slither short distances on land - might get into the Little Patuxent River nearby and spread, devouring native fish.
When the first casualties struggled to the surface gasping, cameramen strained against the yellow police crime tape along the pond bank to record their final moments.
"They're still trying to reach the edge, but what's done is done. They're dead and they just don't know it yet," said biologist Tim Groves, a member of the crew who separated the snakeheads from the other dying fish with a skimmer net.
The bluegills, chain pickerel and crappie - 60 pounds in all - were dumped in a bucket and hauled to a landfill.
However, the carnivorous snakeheads got the royal treatment. Some were dropped in a red bucket to be used as TV props. Others were put on ice and prepared for shipment to scientists and universities around the country that had requested samples.
"If we get an adult, I think there's going to be a long line for it," said Schwaab. "Do we have a decent chance of seeing one? Yeah, but there may only be one."
He got his wish three hours later when biologist Kinte Thompson hauled to the surface an 18-inch adult, perhaps the same one that was caught in May that started the Summer of the Snakehead.
State officials have long maintained that there were originally just two snakeheads - a male and female - dumped in the pond two years ago by a local man when they outgrew his aquarium.
Paul DiMauro caught the first fish May 15, took some pictures and tossed it back, thinking he might have caught an endangered species.
A federal expert in Florida identified a photo e-mailed from the DNR on June 17. Two weeks later, local angler Joe Gillespie turned in a 26-inch fish and said he had hooked one "the size of a golf bag" in April.
No fish that size showed up yesterday.
"That's one piece of the puzzle that doesn't match up," Schwaab acknowledged. "It could be another species. But who knows? Nothing is certain about this."
The two smaller nearby ponds also were poisoned, but nothing floated to the surface.
By the end of the day, DNR biologists had collected more than 120 juvenile snakeheads. Today, they'll place in the pond small traps with sentinel fish - "the canaries in the coal mine," as Schwaab called them - to determine whether the poison dose was lethal and whether they missed any spots.
The poison will dissipate over the next week, and biologists will "electro-shock" the pond this fall to ensure that no snakeheads survived. They will jolt the water with electricity to stun any remaining fish and cause them to float to the surface.
Next spring, if the eradication effort worked, the state will fill the pond with fish from its hatcheries. "Obviously," said Schwaab, "we'll restock with naturally occurring species."
Staff writer Lynn Anderson contributed to this story.