Kyle Glover, the son of Usher's ex-wife Tameka Foster, was enjoying a day on Atlanta's Lake Lanier, riding on an inner tube with a teenage girl, when they were struck by a man riding jet skis on Friday, according to police.
Glover was hit in the head and was unresponsive at the scene and was airlifted to an Atlanta hospital, according to officials.
The girl sustained a broken arm and a laceration on her head, according to ABC News affiliate WSB, and was also airlifted to the hospital.
"Looks like they were just trying to have a good time on the lake and obviously something went wrong," said Sgt. Mike Burgamy of the Department of Natural Resources.
Usher and his ex Tameka Foster have made headlines this year amid a bitter custody dispute over their two children, but TMZ reports this tragedy has brought them together. The star entertainer chartered a plane for Foster, who was out of town, so she could race to her son's side.
For Usher, the incident is the latest in a string of difficult events. After the bitter divorce, last month Usher had to call 911 and get a restraining order after a trespasser/stalker incident in which a woman got into his gated community, camped out on his front stairs and rang his doorbell repeatedly.
While now divorced from the mother of his children, Usher recently told ABC's Robin Roberts he takes fatherhood very seriously.
"My steadfast belief is that a father is important in a child's life," he said.
And now this latest tragedy is threatening the life of his stepson.
Some of Usher's powerhouse music pals have taken to twitter to offer support.
Fantasia tweeted, "Everyone please pray for Usher and Tameka's son! This is the time they really need your prayers."
Russell Simmons tweeted, "praying Usher and Tameka's son is ok…"