Marcel Rodriguez felt a sharp sting on his forearm as he raised his camera to snap a few shots of Tonto National Bridge early Friday morning.
Then he noticed blood seeping through his cardigan.
"I looked at my arm and there was a BB stuck in it," said Rodriguez.
Rodriguez, from Springdale, Utah, sustained a single wound and was treated on the spot.
Meanwhile, Gila County Sheriff's deputies rounded up 19 juveniles hanging out in Tonto Natural Bridge State Park.
"The one who actually discharged the weapon was a 15-year-old female," Undersheriff Adam Shepherd said.
Detective Brian Havey said he collected school identifications, suggesting that some of the juveniles attended Westwood High School and Powell Junior High School in Mesa.
"They were on their last day of school break," Havey said. "And they mistakenly took a BB into the state park where they were shooting a pool of water."
The juveniles received a lecture, and then were released. Possessing weapons in a state park, Havey added, is a Class 6 felony.
Rodriguez, vacationing in northern Arizona, declined to press charges.
"I think it was a random shot and I wanted to get on with my trip," Rodriguez said. "I have never been big on guns, but I'm particularly upset about kids having guns unsupervised."