The Montgomery County retention pond where 10-year-old D’Angelo McMullen died. (Dan Morse/The Washington Post)

The parents of a 10-year-old boy who died in January after falling into an icy pond in Montgomery County have sued several real estate and construction-related companies, asserting that they failed to keep a mandatory fence around the pond that would have kept the child out.

“Had the defendants acted properly, D’Angelo McMullen would not have died,” the parents’ attorney, Andrew G. Slutkin, wrote in a complaint filed in Montgomery Circuit Court on Wednesday.

The parents are seeking millions of dollars in damages, Slutkin said.

On Jan. 13, D’Angelo, his brother and a friend approached the pond near their townhouse development. D’Angelo, who had developmental delays caused by a chromosome disorder called mosaic trisomy 8, walked onto the icy surface. Because he was the youngest and lightest, the ice supported him for a while.

Then it broke, and he fell into the water.

D’Angelo McMullen (Family photo)

D’Angelo’s brother and friend tried to rescue him, but the ice wouldn’t support them, Slutkin said. D’Angelo was underwater for 30 minutes before rescue workers found him and pulled him out.

The loss has devastated his brother. “He couldn’t save him,” Slutkin said. D’Angelo’s mother, Nicole Bode, arrived at the pond during the emergency and witnessed the search-and-rescue effort.

The lawsuit spells out a series of construction approval steps taken by the city of Gaithersburg. At issue is a large development of houses, apartments and stores near the interchange of interstates 270 and 370. Part of the construction involved building a sediment and stormwater pond. The body of water was supposed to be surrounded by a barrier during construction, according to the lawsuit and Gaithersburg officials.

“It’s called a safety fence for a reason,” Slutkin said.

The lawsuit asserts that the city mandated specific measurements: “The fence must be at least 42 inches high, have posts spaced no further apart than 8 feet, have mesh openings no greater than 2 inches in width and 4 inches in height, with a minimum of 14-gauge wire.”

Representatives for three of entities named in the lawsuit could not immediately be reached to comment. They are VII Crown Farm Owner LLC; Sunbrook Partners LLC, doing business as Westbrook Properties; and Warner Construction Consultants.

Michael Post, the president and chief executive of the fourth defendant, Shirley Contracting, said in a statement that the firm shared “the community’s grief over the tragedy that took the life of D’Angelo McMullen on January 13th, and our thoughts and prayers are with his family.”

He said the firm was obtaining a copy of the lawsuit and disagreed with the reported claims in it. We “will be working with legal counsel to provide an appropriate response,” Post said.

Slutkin said he thinks the fence was installed but improperly removed.

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