According to the Texas Department of Public Safety, 27-year-old Officer Blademir Viveros did not have his emergency lights at the time of the deadly crash.
The victims, identified as 53-year-old Angela Stewart, a Houston ISD counselor, and her 16-year-old son Mason Stewart, were hit by the Missouri City police car on June 20 after an officer received a call of a robbery in progress.
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Viveros was said to be driving over the posted speed limit in the 1600 block of Cartwright Road.
The officer was responding to an ATM robbery and was heading eastbound in the 16-1700 block of Cartwright Road when the Stewarts pulled out of a Dollar Tree parking lot.
Police said that's when the officer T-boned their vehicle.
In a release on Thursday, Missouri City PD said the Stewarts failed to yield the right of way before being hit by the police car.
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Authorities told ABC13 that hours after the crash happened, a person was found in the back of the police cruiser.
The person in the backseat of the cruiser has been identified as 53-year-old Michael Hawkins.
His caretaker told ABC13 that he was having unusual behavior that night, so she called 911, leading him to be in the back of the cruiser at the time of the crash.
However, police haven't been able to explain why Hawkins was in the back of the patrol car or why it took so long to discover he was there. Last week, police said they are still investigating why he was in the cruiser as it goes against policy for officers to respond to calls if they already have someone in custody.
Court records show he will be hospitalized for "the foreseeable future."
The lawsuit claims Viveros put Hawkins in danger by not activating his lights and sirens, speeding, and more. It also claims Missouri City police did not properly train and supervise employees.
Police said Hawkins was taken to Ben Taub Hospital, where he is still being treated. Hawkins' friends told ABC13 he is paralyzed from the waist down and is on life support at the hospital.
Video shows first responders frantically pulling him out of the cruiser to give him aid.
Missouri City police said the officer has been with the department for just under a year. He came to Missouri City from a prior agency, where he had about two years of experience.
Viveros has since been relieved of duty as the investigation continues.
RELATED: Missouri City PD officer relieved of duty for crash that killed mother and teen son, department says
Missouri City PD officer relieved of duty for crash that killed mother and teen son, department says