Riders on the Shock Wave roller coaster at Six Flags Over Texas in Arlington were escorted safely off the ride Friday morning after it got stuck.
One rider, Andrew Cook, took time to take a selfie and posted it on Twitter about 11:15 a.m. before workers helped riders down steps to the bottom of the ride.
Sharon Parker, a park spokeswoman, said the ride stopped midway up the lift to the top after a computerized system detected an error.
There were about 20 riders on the coaster, and they were stuck for about 30 minutes, Parker said.
The Shock Wave was closed indefinitely for inspection, Parker said.
The rest of the park remains open.