(CBS4) - A second person has died after last weekend's crash involving a vehicle and a Denver fire truck. Debra Williams, 53, was the passenger in a Honda Civic that was involved in a collision with a fire engine on Saturday, at the intersection of Speer Boulevard and Broadway. Firefighters were responding to a call and the truck had its lights on and sirens blaring.

The driver Monica Charles, 38, died that day. A third person in the car was also was hurt.

A witness told CBS4 it appeared the driver of the car was trying to beat the fire truck through the intersection.

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Police are investigating the operation of a system called Opticom that is supposed to change stoplights when an emergency vehicle approaches.

No firefighters were injured.