CHICAGO (CBS) — Three children were injured by a lightning strike Thursday morning in north suburban Round Lake Heights.

A group of children was waiting at a bus stop around 7:20 a.m., and sought shelter from the rain under a tree, when lightning struck nearby, school and fire officials said. It was not immediately clear if the lightning struck the tree itself, or the ground nearby. The Greater Round Lake Fire Protection District responded to reports of the lightning strike, and firefighters arrived to find three children lying on the ground near the tree.

Charlene Monk raced to the scene after learning her daughter, 13-year-old Carrington, had been struck by lightning. When she arrived, Charlene saw her daughter being loaded into an ambulance.

“Wow. I was terrified, and in shock, and panicked, and started driving faster,” she said.

Carrington was stabilized at Advocate Condell Medical Center, and was able to tell her mother about her ordeal.

“She just told me that she was standing under a tree, her and the other two girls, to shield themselves from the rain,” Charlene Monk said. “All of a sudden the lightning struck, and they all fell.”

Carrington was knocked unconscious, but will be okay. Her mother said she will stay in the hospital overnight for observation.

The other two children also were being treated at Condell. Their injuries were not life-threatening.

The other victims’ ages were not immediately available.

Lake Villa School District 41 Supt. Alex Barber said the three injured children are students at Palombi Middle School. He said they were waiting for a bus with six other students, when lightning struck nearby.

The students who were not injured were either taken to school, or went home with their parents.