Minnesota Vikings running back Adrian Peterson is in mourning after the death of his young son Friday, and words of support poured in from the sports world. The authorities said the 2-year-old boy died of injuries sustained in a child-abuse case in South Dakota. The death was confirmed by the Lincoln County, S.D., state's attorney Tom Wollman. The boy, who had been in critical condition in a hospital with severe head injuries since Wednesday, died at 11:43 a.m. after being removed from life support, Wollman said. Joseph Patterson, 27, was reportedly dating the mother of the child. He was charged with aggravated assault and aggravated battery in the death. Peterson, who declined to talk about the case after practice Friday, said he was certain he would play Sunday against Carolina. "I'll be ready to roll, focused," he said. Peterson is second in the N.F.L. with 421 rushing yards and first in the league with five rushing touchdowns. He came back from reconstructive knee surgery to rush for 2,097 yards and win the league's Most Valuable Player award last season. Later Friday, after news of the death spread, Peterson thanked his family, his fans and the fans of other teams for their support, writing on Twitter: "The NFL is a fraternity of brothers, and I am thankful for the tweets, phone calls and text messages from my fellow players." Dozens of current and former professional athletes wished Peterson well on Twitter. "Sick for my friend," the N.B.A. star LeBron James wrote. Strong guy but this one will bring the strongest down. Panthers Coach Ron Rivera said: "It's absolutely terrible. Our thoughts and prayers go out to him and his family. SUH FINE UPHELD Detroit Lions defensive tackle Ndamukong Suh lost an appeal of a $100,000 fine for a block below the belt, the sixth fine of his four-year career. The fine was the largest in N.F.L. history for on-field conduct, not including money lost by players because of suspensions. It surpassed the $87,500 that Chicago Bears linebacker Bryan Cox was docked in 1996 for making an obscene gesture to a line judge and screaming obscenities. Suh was fined two days after an illegal block on Vikings center John Sullivan in a season-opening win. Suh apologized to Sullivan and to his teammates. The penalty negated an interception return for a touchdown. A star at Nebraska, Suh was the No. 2 overall draft pick in 2010, after quarterback Sam Bradford.