A massive boulder that dislodged from a mountain in Arizona sparked a dramatic helicopter rescue after it bowled over a group of teenagers hiking in its path.

The five students from Agua Fria High School in Avondale, Ariz., were hiking in the White Tank Mountains Wednesday when they veered from one of the mountain's popular trails to go on their own unmarked path, Maricopa County Sheriff's officials said.

A boulder described by rescue crews as possibly weighing more than 700 pounds became dislodged and tumbled from the mountain and towards the students, knocking them down as it rolled over the group.

Nick Pimentel, 18, was the only one of the five students who wasn't knocked down by the boulder and called 911 to help.  He said one of the teens tried to stop the boulder before it struck others in the group, but was knocked down by the huge rock,  according to local ABC affiliate KNXV TV.

"That was my main goal…to keep them safe up there," Pimentel told KNXV of his actions.

A Department of Public Safety rescue helicopter was dispatched to rescue the teens. A 17-year-old girl had to be pulled up into the chopper with ropes and a harness because she suffered a broken leg and could not walk.  She was later airlifted to a hospital for treatment.

The three other injured teens suffered non-life threatening arm and leg injuries, the sheriff's office said.

The Associated Press contributed to this report.