A 15-year-old Maria Carrillo High School student pedaling to school Thursday morning slammed into a Santa Rosa fire engine as it backed into its Calistoga Road station, authorities said.

The boy, Sean Kim, escaped major injury despite the mangled bicycle and shattered helmet he left behind, Police Sgt. Doug Schlief said.

"It's unknown if there's any fractures or anything, but the bicyclist is being treated right now, and it's nothing significant, thank goodness," Schlief said shortly after 11 a.m.

Authorities said Kim was cycling northbound in a southbound bike lane, heading toward school and the fire station on the west side of Calistoga Road as a four-person company aboard Engine 6 returned from a medical call around 7:30 a.m.

The driver, fire engineer Peter Blake, pulled to the west-side curb then pulled forward into the southbound lane and began backing into the station across from Marit Drive, Schlief said.

Kim later told police he saw the firetruck across the bike lane in front of him, its lights flashing and back-up tone beeping, Schlief said.

But he thought the engine would back in more quickly and that he could get around the front of it, he told police.

Instead, he struck the engine behind the right front tire and slid onto his side. The engine tire rolled over the front of the bicycle and pinned him to the ground, Schlief said.

Another firefighter was serving as "backer," standing in the driveway and guiding Blake back toward the bay per department protocol, police and fire officials said.

Neither saw Kim, and the crew was unaware of him until they heard him scream and the sound of the collision, Schlief said.

Blake quickly stopped the engine, preventing it from rolling over Kim. The cyclist was not wearing the helmet he had with him, but there was no head injury, Schlief said.

Information about the extent of any injury to the cyclist was not known.

Fire Chief Bruce Varner said the crew provided medical aid to Kim, who was taken by ambulance to Santa Rosa Memorial Hospital.