The collision resulted in a fire and explosion that damaged Carroll College and other nearby structures, knocked out power to most of the town, and led to the evacuation of residents within an area of 2 square miles (5.2 km2) due to concerns of possible toxic chemical release.
The event occurred during a severe cold snap, with temperatures below −30 °F (−34 °C) that morning and with a wind chill factor of as much as −75 °F (−59 °C), which froze the water that firefighters used to attempt to extinguish the fire.
Halfway up the pass, the lead engine developed an electrical problem that caused a loss of power (and failure of the cab heater) and at about the same time was stopped by a malfunctioning signal.
[2] The cars then rolled backwards 9 miles (14 km) downhill, uncontrolled, into Helena, crashed into a parked work train near the Benton Avenue crossing and Carroll College, caught fire, and exploded.
[5] No one was killed, but the explosion disabled electric service to much of the community, as well as to some residents outside Helena, including rolling brownouts extending as far north as Great Falls, Montana, approximately 90 miles (140 km) away.
[4] Later consequences included water damage to buildings resulting from frozen plumbing and other difficulties that necessitated expensive repairs and plagued local residences for years.