Durham prosecutors say the woman attempted to start a fire at the same apartment complex a week earlier.
The 38-year-old is facing charges in Wake County for a home that was set on fire in northeast Raleigh.
Police say the firefighter was combative with responding officers and was placed under an involuntary commitment.
The deputy fire chief was responding to suspected arson when the crash occurred Friday night.
The post office building caught fire and was engulfed in flames after the car went into it.
One of the teens was a lifeguard at the Edgebrook Eels Swim Club in Garner.