Illinois Rep. Sean Casten's 17-year-old daughter, Gwen, died Monday morning, his office confirmed.
In a short statement shared on Twitter on Monday night, his office said the lawmaker's "beloved daughter, Gwen (17) passed away."
"The Casten family requests privacy, and we will be issuing no further comment during this heartbreaking time," it said.
Casten's office did not provide any details on the cause of death.
The teenager had recently appeared in a campaign video supporting her father's bid for a third term in Congress.
In the video, released earlier this month, she spoke of how turning 18 would be a “big year” filled with “lots of milestones,” including “voting for the first time. But not just for anyone.”
"Sean Casten. My congressman. But I just call him dad," she said in the video, in which she championed her father's efforts on new gun laws and and protecting abortion access.
Casten, a Democrat, represents Illinois’ 6th Congressional District. He was first elected in 2018 and was the first Democrat to represent the district in nearly 50 years.
Tributes and words of support poured in for Casten's family in response to his office's announcement.
" Illinois state Rep. Bob Morgan wrote in a tweet. "You and your family are in my prayers, and I hope you find strength in the difficult days ahead. May Gwen’s memory be a blessing upon us all."