Maeve Kennedy Townsend McKean’s husband has posted a heartbreaking tribute to his wife—the granddaughter of the late Sen. Robert F. Kennedy—and the couple’s child, who went missing in the Chesapeake Bay Thursday afternoon.

The Kennedy family announced Friday that the Coast Guard suspended the rescue effort for McKean, 40, and son Gideon, 8, who disappeared after paddling a canoe out into the bay. The effort to recover their remains is ongoing.

“The search that began yesterday afternoon went on throughout the night and continued all day today,” McKean’s husband, David McKean, wrote in a Facebook post late Friday. “It is now dark again. It has been more than 24 hours, and the chances they have survived are impossibly small. It is clear that Maeve and Gideon have passed away.”

The family had been self-quarantining from the novel coronavirus in a house on the bay owned by McKean’s mother, former Maryland Lieutenant Governor Kathleen Kennedy Townsend, according to her husband’s post. The largely empty house provided them with more space to ride out the pandemic than their D.C. home, he said.

McKean and her son were playing on a beach in a small, shallow cove behind the house at around 4 p.m. when one of them accidentally kicked a ball into the water. The two attempted to retrieve the ball by paddling a canoe into the protected cove, but ended up in the open bay where strong winds during the day had whipped up vicious currents.

“The cove is protected, with much calmer wind and water than in the greater Chesapeake,” David McKean wrote. “They got into a canoe, intending simply to retrieve the ball, and somehow got pushed by wind or tide into the open bay.”

About 30 minutes later, an onlooker called emergency services to report seeing the pair struggling to paddle to the shore. That was the last anyone saw of them. The Coast Guard recovered their capsized canoe miles away from the beach at 7 p.m. Friday.

David McKean wrote tenderly of his late son, recalling his love of sports and strong morals.

“He was deeply compassionate, declining to sing children’s songs if they contained a hint of animals or people being treated cruelly,” he wrote. “And he was brave, leading his friends in games, standing up to people who he thought were wrong (including his parents), and relishing opportunities to go on adventures with friends, even those he’d just met.”

“I used to marvel at him as a toddler and worry that he was too perfect to exist in this world,” he added. “It seems to me now that he was.”

His wife, McKean wrote, was “magical,” with “endless energy” and a laugh you could hear a block away.

“Maeve turned 40 in November, and she was my everything,” he wrote. “She was my best friend and my soulmate. I have already thought many times over today that I need to remember to tell Maeve about something that’s happening. I am terrified by the idea that this will fade over time.”

The couple met while working for Sen. Dianne Feinstein (D-CA) and were married in 2003. Maeve served in the Peace Corp, with the State Department’s global AIDS program, and in the Obama administration’s Department of Health and Human Services, before signing on as executive director of the Georgetown University Global Health Initiative.

“Maeve was vivid,” her mother, Kathleen Kennedy Townsend, said in a statement Friday night. “You always knew when she was in a room. Her laughter was loud, unabashed and infectious.”

McKean’s cousin, Rep. Joe Kennedy III (D-MA), posted on Twitter: “We love you Maeve. We love you Gideon. Our family has lost two of the brightest lights.”

McKean is survived by her 7-year-old daughter, Gabriella, and 2-year-old son, Toby. “I know soon he will start to ask for Maeve and Gideon,” her husband wrote of Toby. “It breaks my heart that he will not get to have them as a mother and brother.”

In his Facebook post, David McKean asked friends and family to share photos of his late wife and son.

“As Gabriella and Toby lay sleeping next to me last night, I promised them that I would do my best to be the parent that Maeve was, and to be the person that Gideon clearly would have grown up to be,” he wrote. “Part of that is keeping their memories alive.”

The Kennedy family has endured an extraordinary amount of tragedy over several generations, from the high-profile assassinations of McKean’s grandfather and great-uncle to the fatal plane crash that killed John F. Kennedy Jr., to the heart attack that killed Robert F. Kennedy Jr.’s niece, Kara, in 2011 and the death by suicide of his ex-wife, Mary, in 2012.

Just last year, McKean’s cousin, Saoirse Roisin Kennedy Hill, died of an accidental drug overdose at the Kennedy family compound in Cape Cod.