Usher has been left "completely devastated" after his 11-year-old stepson was declared brain dead.

The rapper is said to feel "distraught" after doctors revealed Kyle Glover - the child of the singer's ex-wife Tameka and her former partner Ryan Glover - "not experienced any brain activity" since being admitted to hospital on Saturday (07.07.12) after he was struck on the head by a jet ski in Lake Lanier in Atlanta, Georgia.

A source close to 33-year-old rapper told HollywoodLife.com: "Usher is completely devastated and shaken with what has occurred.

"[He] is emotionally drained from the accident. He feels incredibly awful, distraught...it's been a complete rollercoaster of emotions."

Kyle was riding on an inner tube in the lake when he was struck by the passing jet ski, and following the incident he was admitted to the Children's Healthcare unit at Egleston Hospital in Atlanta.

Tameka was "extremely thankful" to Usher after he reportedly chartered a plane allowing her to fly to Atlanta to be at Kyle's side, and she has taken to her Facebook page to thank fans for their support and urge them to pray for her son.

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)"

A decision has yet to be made on whether to take the youngster off life support, and the incident is now being investigated.