The search for Maeve Kennedy McKean and her eight-year-old son Gideon "has turned from rescue to recovery," Kennedy McKean's mother said in a statement Friday night. The pair were last seen in a canoe off Chesapeake Bay on Thursday evening.

"With profound sadness, I share the news that the search for my beloved daughter Maeve and grandson Gideon has turned from rescue to recovery," said Kathleen Kennedy Townsend, daughter of Robert F. Kennedy and former Maryland lieutenant governor.

"My heart is crushed, yet we shall try to summon the grace of God and what strength we have to honor the hope, energy and passion that Maeve and Gideon set forth into the world," Kennedy Townsend said. "My family thanks all for the outpouring of love and prayers as we grieve and try to bear this devastating loss."

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Massachusetts Congressman Joe Kennedy III, Kennedy McKean's cousin, shared his grief on Twitter.

We love you Maeve. We love you Gideon. Our family has lost two of the brightest lights. Grateful for the prayers. Hold your loved ones tight. — Rep. Joe Kennedy III (@RepJoeKennedy) April 4, 2020

A statement from the Maryland Natural Resources Police, which is leading the investigation, said Friday that a "preliminary investigation revealed that the pair may have been paddling the canoe from a residence in Shady Side, MD out into the bay to retrieve a ball and were unable to paddle back to shore."

Anne Arundel Fire Captain Erik Kornmeyer said that, despite arriving within five minutes of the call, the fire dispatch was unable to reach the canoe. "Currents were pretty fast, they moved out of sight pretty quickly," he said, adding that conditions were "rough and windy" on Thursday night.

Boats and helicopters from the fire department, the City of Annapolis Fire Department, and the United States Coast Guard quickly began to search the bay, Kornmeyer said. Over two hours later, at 7 p.m., a canoe and paddle were found several miles from where Mckean and her son were first spotted.

"At approximately 7:00 p.m., an overturned canoe, matching the approximate description of the one which the pair were in, was located," the Natural Resources Police said.

Maeve Kennedy McKean Getty Images

The U.S. Coast Guard and a fireboat from the City of Annapolis Fire Department found the canoe and paddle east of Rockhold Creek in Deale, Maryland, near Herring Bay, according to the Anne Arundel County Fire Department press release. The search was called off at 7:30 p.m. "due to darkness," and resumed early Friday morning.

The National Weather Service said conditions will be hazardous to small craft on Chesapeake Bay all day Friday. The NWS issued a "small craft advisory" for the bay until midnight Friday, citing 15 to 20 knot (nautical miles per hour) winds, gusts of up to 30 knots, and three feet waves this afternoon, with similar conditions into the evening.

The Coast Guard said Friday night they were ending their role in the search for the pair, a source familiar with the matter told CBS News.

"We are looking at a situation where they may never be recovered," said the official, who was granted anonymity to speak frankly about the ongoing search.

Pat Milton and Ed O'Keefe contributed reporting.