Stuart Mazanec died Wednesday from organ damage, four days after the accident at a weekend rodeo clinic in Byers, about 30 miles east of Denver.
"It was his first and last ride," said his mother, Pam Mazanec.
Stuart Mazanec, a senior at Douglas County High School south of Denver, was trying to get off the bronco after finishing the standard 10-second bareback ride Saturday when his hand got caught in the rigging around the horse's neck, said Jay Brentner, a family friend and rodeo veteran who was at the clinic.
Mazanec tried to run alongside the horse, but the animal staggered, tripped and landed on him. When the horse got up, the teen was hanging limply at its side, Brentner said.
After being taken to a Denver hospital, Mazanec managed to speak despite a broken jaw, his mother said.
"The first thing he told me was, 'Mom, don't cry,"' she said.
By Wednesday, his body had begun to fail, and the family decided to remove life support that night after consulting with doctors and a priest, Pam Mazanec said.
Pat Bohlender-Lowe of the Colorado State High School Rodeo Association said she could recall only one other youth rodeo fatality in the state, a bull-riding accident about 20 years ago.
"People sometimes forget what a rough sport it is," said Brentner. "But for Stuart, the one thing he always wanted to try ended up being the thing that killed him."