A medical episode behind the wheel led to a chain-reaction crash on U.S. Highway 281 near Bitters Road on Saturday afternoon, according to San Antonio police.

Surveillance video from a nearby business captured the moment a Toyota Highlander driver lost control on the access road, struck a TxDOT sign and crossed into the northbound lanes of the highway.

The SUV then hit a Dodge Ram, which struck a Chevrolet Suburban before rolling several times.