It began in southwest Houston around 3 a.m.
Medics were on their way to a hospital with a patient onboard when the man, who was in another vehicle, forced the HFD ambulance to stop, according to Houston police. That's when he forced the driver out at gunpoint, got in, and drove away.
LISTEN: Gunman radios dispatchers while fleeing with EMT and patient inside HFD ambulance
LISTEN: Gunman radios dispatchers during hijacked HFD ambulance chase
The man opened fire on passing vehicles along the freeway, police said, but no one was hit.
As the ambulance made its way onto another major highway, the EMT, who was attending to the patient in the back, realized something was wrong and checked on the driver, who she then found out was the hijacker, police said.
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The driver threatened that EMT with the gun, but authorities said she worked to keep everyone calm during the ordeal.
"She de-escalated the incident by essentially not panicking," Houston Fire Chief Sam Pena said. "She remained calm throughout the incident."
The EMT alerted dispatchers who were able to track the ambulance as HPD responded. Officers pursued the ambulance across southeast Houston before the driver headed west and made his way into the southwestern part of the city.
Houston police were able to force the gunman to stop the ambulance before he gave up. Officers took the man into custody on the freeway.
No one was harmed during the ordeal, and the patient onboard was able to be moved to another ambulance before finally being taken to the hospital.
The gunman, who was not immediately identified, was under the influence of some kind of substance and has a lengthy criminal history, police said.