Clark tweeted the news Sunday and referred to it as arson.
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
Clark also retweeted a Jan. 30 tweet from the Cleveland Fire Department noting that the bodies of four victims from a fire on the city's east side had been located and recovered.
"The entire Seahawks family is mourning with Frank Clark and his loved ones after their tragic loss," the team said Sunday in a statement. "Our thoughts and prayers will be pouring out to Frank and his family during their time of grieving."
Cleveland.com reported that the fire began at 1 a.m. Tuesday, and investigators are trying to determine the cause of the fire. The report did not specify whether it was arson.
Seahawks teammate DeShawn Shead tweeted his condolences to Clark.
Sorry to hear that bro!! Family and I will be praying for you 🙏🏾🙏🏾
— DeShawn Shead (@dshead24) February 5, 2018
Clark's agent, Erik Burkhardt, offered his support as well.
I love you Frank. We're gonna get thru this. Our whole SSGfam is here for you brother. 🙏🏼
— Erik Burkhardt (@ErikBurkhardt) February 5, 2018
Clark, 24, was a second-round pick by the Seahawks out of Michigan in 2015. He grew up in Los Angeles until age 12, when his mother sent him to live with family members in Cleveland.
Clark has 22 sacks in three seasons with Seattle. He became a starter in October 2017 after Cliff Avril suffered a season-ending neck injury.