Based on the search results, there were a few incidents that happened at Six Flags parks, but there is no information about what happened at Six Flags yesterday. Here are some notable incidents that happened at Six Flags parks:

• On August 25, 2019, five people were taken to the hospital after riding the El Toro roller coaster at Six Flags Great Adventure in Jackson, New Jersey.
• On July 13, 1993, a train collided with another one at the station, causing injuries to eight people at Six Flags.
• On June 8, 2002, a 4-year-old girl was critically injured when she slipped beneath the restraining bar and fell from the Starfish ride while riding with her mother at Six Flags.
• On July 13, 2016, a bomb threat was called in right before the park opened at Six Flags.
• On August 25, 2019, a passengers safety harness malfunctioned when one of the trains began its initial ascent, causing an emergency stop at Six Flags America.

If there was an incident at Six Flags yesterday, it is not mentioned in the search results.