UHP officials said the driver of the eastbound Jeep, from Loa, lost control of his vehicle, and collided with two westbound motorcycles.
The Jeep initially struck Gelernter, also from Tucson, and his Harley motorcycle was pushed off the road.
The Jeep then struck and ran over a Victory motorcycle ridden by the Mitchells. The motorcycle's gas tank ruptured, and the Jeep and motorcycle burst into flames, the UHP reported.
The driver of the Jeep, who was not wearing a seat belt, was ejected.
UHP officials reported that the teen lost control of the Jeep when it drifted left and he over-corrected to the right, running off the right shoulder and striking a guardrail.
The teen then corrected back to the left and crossed the center line into the westbound lanes where he collided with the motorcycles.
UHP officials reported that the Mitchells and Gelernter were riding as a group with two other motorcycle riders. The other riders steered left into the eastbound lane to avoid hitting the Jeep.
According to Gelernter's Facebook page, the group had planned an 11-day trip to ride from Arizona to Utah, Colorado and New Mexico. They had five days left in their trip when the accident occurred.
UHP Sgt. Mary Kaye Lucas said Friday afternoon that the investigation into what caused the Jeep driver to lose control is ongoing. She advised that drivers take extra caution with the warm weather and more traffic on the roads.
"People need to be really vigilant about wearing their seat belts, watching their speeds, and not letting anything distract them," she said.