TRUMBULL -- A 21-month-old boy washed down the rain-swollen Pequonnock River early Wednesday died just before 6:30 p.m., according to Trumbull police.

Tommy Chisholm had been clinging to life in Bridgeport Hospital after the toddler was swept down the river and into Bunnell's Pond in Bridgeport, about a half-mile downstream Wednesday morning.

Tommy, the son of Michael and Ruth Chisholm of 40 Lindberg Drive, was missing for nearly two hours until his unresponsive body was found in the pond.

Deputy Police Chief Michael Harray said the toddler passed away early Wednesday evening.

Police Chief Thomas Kiely said that an older sibling ---- believed to be the child's stepsister in her 20s ---- called 911 at about 10:42 a.m.

"The child, who was nearly two was playing near the river," Police Chief Thomas Kiely said. "The mother had just turned around for a matter of a minute, and the next thing she knew, the child was missing." The mother jumped into the river in an attempt to rescue her son, police said, but it's not known if she even had the child in sight.

Dozens of police, fire, scuba and K-9 units from Trumbull, Shelton, Bridgeport, Monroe and Darien rushed to the scene, searching the river and the woods along its banks. K-9 units used one of the child's stuffed animals to get his scent ---- a little white lamb with black button eyes.

The house, a ranch with an attached two-car garage, borders the river. Neighbors said that the Pequonnock at that point is usually placid and harmless, but it quickly turns angry after the kind on rainstorm that was seen in the early hours of Wednesday morning. About an inch of rain fell between midnight and 7 a.m., according to the National Weather Service.

In addition to searching the river, police dogs scoured the neighborhood and police asked the owners of all of the cars parked in the neighborhood to open their trunks in hopes of finding the tot alive and unharmed.

As the searched progressed, police and firefighters pulled two small blankets and a child's shirt from the raging torrent as it rushed past the thicket at the foot of Lindberg Drive.

"We called out all the resources that the could," Kiely said. We had units from Shelton, Bridgeport, Darien, Monroe. As many divers as we could get and as many K-9 units as we could get."

But in the end, the child was spotted by Bridgeport Parks Department employees, who were told to be on the lookout for anything unusual.

The child ---- who witnesses said appeared to be lifeless when he was pulled from the water at about 12:30 p.m. ---- was transported by ambulance to Bridgeport Hospital.

"The family is distraught, as you can imagine" Kiely said. "We transported the parents to Bridgeport Hospital." Kiely said that the incident is being treated as a tragic accident.

"The water was moving very, very quickly," said Trumbull Center Fire Chief Ed Gratrix. "About nine knots. It was difficult to even stand in it. One thing in the child's favor, though, is that the water is cold."

Gratrix said that a side-scan radar unit from the State Police was also called in, but the child was found before this equipment could be deployed.

"We put out the call for help, and everybody came," Kiely said. "All we can do is hope for the best."

First Selectman Tim Herbst said, "I was impressed with the quick response of the Trumbull Police Department and Fire Department, and I have to commend Chief Kiely and Cheif Gratrix for putting together such a coordinated response."

Herbst also thanked the emergency services from neighboring communities, and the state police, for helping out.

Herbst said that the town will do what it can to support the family. "We're Trumbulites, and we'll be here for them," he said.

Staff writers John Burgeson, Daniel Tepfer and Anne M. Amato contributed to this story.