A 17-year-old player struck the referee, Ricardo Portillo, in the head last week after Portillo penalised the teenager during a game in a Salt Lake City suburb.
The player, whose name was withheld because he is a juvenile, was upset because Portillo had issued him a yellow card.
Portillo, 46, of Salt Lake City, was taken by ambulance to a hospital to be treated for what was initially believed to be minor injuries. It was later determined that Portillo had suffered more substantial head trauma.
He lapsed into a coma before dying one week after the incident.
The teenager is being held at a juvenile detention facility on suspicion of aggravated assault, a felony. The player is expected to be formally charged next week.
Unified police spokesman Justin Hoyal said. "The suspect was close to Portillo and punched him once in the face as a result of the call."
Portillo's daughter, Johana Portillo, told a news conference on Thursday that the player "just came out of nowhere" and punched her father.
"I know if he spends time in jail, like forever, it's not enough," she said. "It's not going to bring my daddy back."
Officials with the American Youth Soccer Organisation, the nation's largest football association for players aged four to 18, said they did not know of another such incident in the history of youth football in the United States.
Portillo was refereeing a match put on by a league called La Liga Continental, which is not affiliated with the American Youth Soccer Organisation.
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