Five EMS workers were inside the ambulance tending to a patient when the accident happened at around 4am on Holman near Saint Charles.
"A vehicle traveling at a very high rate of speed crashed into the ambulance," said Sgt. Kerry Shaw with the Houston Police Department.
Police said the driver of the silver Dodge SUV made no attempt to stop prior to the crash and was killed instantly.
"The ambulance was parked headed eastbound in the westbound lane, but he had his emergency equipment on and that's perfectly fine to do," Shaw said.
The impact was so severe it pushed the ambulance unit into a fire department squad unit that was parked behind it.
Inside the ambulance, the EMS driver and family member of the patient sat in the front while four firefighters were attending to a possible heart attack patient in the back of the vehicle.
Police tell us all seven were taken to local hospitals with injuries. Two firefighters involved have already been released from the hospital. Two more are expected to be released later today. One firefighter will remain in a hospital because of injuries to his leg.
"The most severe injury from what we are being told right now is one of the firemen has a possible broken leg," said Shaw.
The patient and the family member of that patient were also transferred to the hospital. They are listed as stable.
Jay Evans with the Houston Fire Department says they are fortunate nobody was injured more severely in this wreck.
"Everyone is going to be OK," said Evans.
The identity of the driver of the silver Dodge SUV hasn't been released. At this point, whether or not alcohol was involved in this accident will be determined during the autopsy of the deceased driver.