The Illinois Department of Natural resources said the girl, who is from Zion, was swimming in the lake at the state park with her family. At about 5:45 p.m., she went missing in the water and her 14-year-old brother tried to find her.
When he couldn't, the family called 911, officials said. Soon, emergency crews took to boats and helicopters to find and pull that teenage swimmer out of the water.
"We saw the girl coming out, like, twice, and then we lost her and that's when I started panicking," said witness Silvia Mejia. "I saw someone screaming and I looked in that direction, and i saw this boy calling for help. So, I started screaming, like, 'Somebody's drowning! Somebody's drowning!'"
Christian Tortorello said he also swam out to help crews, using a life ring to help crews pull the girl to shore.
"I did what I could do with swimming out there. That's the best I could do because I'm not that good of a swimmer," he said.
"My prayers are with them, and then hopefully God brings peace to their hearts because I know I'm a mother, too, so I know how difficult it might be to go through this," Mejia said.
Authorities said the girl did regain her pulse while en route to Vista East Hospital in Waukegan, where she is in critical condition.