Tameka Foster and Usher

Usher's 11-year-old stepson has been declared brain dead after a Jet Ski accident this weekend, TMZ reports.

Kyle Glover, the son of Usher's ex-wife Tameka Foster, was riding an inner tube on Lake Lanier in Atlanta Friday with a 15-year-old girl when they were struck by a passing Jet Ski, knocking Glover unconscious. According to TMZ, Glover has not shown any brain activity since being admitted to Atlanta's Egelston Hospital. The girl has been treated for injuries.

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Usher and Foster are both at Glover's bedside, and no decision has been made about whether to take him off life support, the site says. Neither has publicly commented on the accident.

The Georgia Department of Natural Resources is investigating the accident and has ruled out alcohol as a factor. A DNR rep told The Atlanta Journal-Constitution that the man riding the Jet Ski and the children tubing were part of the same group on an outing at the lake.

Usher and Foster divorced in 2009 after two years of marriage.