A 16-year-old boy suffered a cardiac arrest and five others were hurt in a lightning strike in a Birmingham park.
The teenager is in a critical but stable condition following the incident in Small Heath Park at 1650 BST, said West Midlands Ambulance Service.
Five other teenagers were also taken to hospital. It is believed three are still in hospital under observation.
A spokeswoman for the ambulance service said it received several 999 calls following the incident.
She said five ambulances were sent to the scene as well as a rapid response motorcycle, an incident support officer and a senior paramedic manager.
"Crews arrived at the park to find a teenage boy receiving CPR from a member of the public," she said.
"The 16-year-old boy suffered serious burns after being struck by lightning and was in cardiac arrest.
"Crews continued emergency medical treatment on the boy and transferred him by land ambulance to Heartlands Hospital."
A second teenage boy suffered convulsions consistent with an electric shock and was treated at the scene before he was also taken to Heartlands Hospital.
The four other teenagers suffered minor injuries and were assessed at the scene before three were taken to City Hospital and one to Heartlands.