"My father was killed in an arson fire along with three other members of my family on the East Side of Cleveland," the 24-year-old Clark tweeted on Sunday. "Pray for me and my family during this time."
Clark also retweeted a post from the Cleveland Fire Department that said the bodies of four victims from a fire on the city's east side had been located and recovered. It reportedly was the deadliest fire in the city since 2009.
"The entire Seahawks family is mourning with Frank Clark and his loved ones after their tragic loss," the team said in a statement. "Our thoughts and prayers will be pouring out to Frank and his family during their time of grieving."
My father was killed in an arson fire along with 3 other members of my family on the East Side of Cleveland. Pray for me and my family during this time. pic.twitter.com/bjXxHCRe4n— Frank Clark (@TheRealFrankC_) February 4, 2018
Per Cleveland.com, the fire began early Tuesday morning, although investigators have yet to determine the cause of the flames. It also did not specify whether the fire was arson.
Alfonso Lathan Jr., 46, his three-year-old son Alfonso III, his eight-year-old granddaughter, Nyiah, and his 44-year-old nephew -- who was not named -- were listed among the victims. Alfonso Lathan's wife, Gianna, escaped the blaze by jumping out of a second-story window.
Clark, who was originally from Los Angeles, lived in Cleveland after his mother sent him to live with family members.
He recorded 32 tackles and 9.0 sacks this season to increase his career totals to 95 and 22.0, respectively, during his three years with the Seahawks. He was selected in the second round of the 2015 NFL Draft by Seattle.