(USA TODAY) -- Sad news: Usher's 11-year-old stepson is in critical condition after the inner tube he was riding Friday on Georgia's Lake Lanier was struck by a Jet Ski driven by a 38-year-old man, reports Atlanta's 11 Alive News (like USA TODAY, a Gannett-owned company).

Kyle Glover, whose mom is the singer's ex-wife, Tameka Foster, was sitting with a 15-year-old girl in the inner tube, which was being pulled along by a boat.

TMZ reports that the boy was hit in the head and was unresponsive when taken out of the water. The girl also suffered serious injury.

Officials told 11 Alive that alcohol did not play a role in the accident and that it was too soon to know if any charges will be filed.

Despite the couple's ongoing and acrimonious custody fight, Usher chartered a plane to whisk Foster to her son's side, TMZ says.

Usher's famous friends are tweeting their concern. Writes Russell Simmons:

"Praying that Usher and Tameka's son is ok... "

Echoed Fantasia Barrino: "Everyone PLEASE pray for Usher and Tameka's son! This is the time they really need your prayers!"

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