Los Angeles - Usher's 11-year-old stepson has been declared brain dead by doctors.
Kyle Glover - the child of the singer's ex-wife Tameka Foster and her former partner Ryan Glover - was unresponsive when he was rescued from Lake Lanier in Atlanta, Georgia, on Saturday after being struck on the head by a passing jet ski while riding on an inner tube and taken to the Children's Healthcare unit at Egleston Hospital in Atlanta but has "not experienced any brain activity" since being admitted, a source told gossip website TMZ.com.
A decision has yet to be made on whether to take the youngster off life support.
Tameka took to her Facebook page to thank fans and family for their support and urged them to pray for her little boy.
The mother-of-five wrote: "Kyle, You are strong ... You'll be saved I know it. I love you my baby. I need all #Prayers for my son! thanks you everybody! (sic)"
Tameka - who has been undergoing a bitter custody battle with Usher over their sons Usher VI, four, and Naviyd Ely, three - was "extremely thankful" to her former spouse after he reportedly chartered a plane for her to fly back to Atlanta to be by Kyle's side.
A 15-year-old female companion is also reported to have been struck by the jet ski, though her condition is not serious.
The accident is now being investigated, with the Department of Natural Resource in Atlanta launching an inquiry.
A spokesperson for the organisation confirmed rangers have been in touch with the jet ski driver.
Once the investigation is completed, a recommendation will be given to the district attorney, who will decide whether to file any criminal charges.