The Dallas County district attorney’s office announced Wednesday that it would undertake a full review of the events surrounding the death of Graham Dyer, an 18-year-old who died nearly four years ago in the custody of Mesquite police officers.

The development comes less than a week after an American-Statesman article described how his parents fought for more than two years to get police records describing what happened to their son on the night of Aug. 13, 2013. Texas law allows law enforcement agencies to withhold their investigative files if a case doesn’t result in a conviction. Because Graham died, Mesquite officials told Kathy and Robert Dyer they couldn’t have files and videos documenting their son’s final hours.

When the Dyers eventually did obtain the videos through persistence and a backdoor method to work around Mesquite’s refusal, the images were disturbing. In one, Graham, who was having a bad reaction to LSD, can be seen hurling himself around the back of the police cruiser. Experts said officers should have taken greater care to prevent him from hurting himself.

In another, police can be seen shocking the handcuffed and leg-shackled Graham with a Taser, apparently deliberately, in his testicles while he screams in pain. An officer can be heard saying: “Mother(expletive), I’m going to kill you.”

RELATED: Texas police withheld records of their son’s death. Now they know why.

And while police had told Robert and Kathy Dyer that Graham had needed to be placed in a restraint chair after being delivered to the jail, a video of the 5-foot-4-inch, 110-pound teenager shows him lying limply on the ground after being lifted out of the police car, seemingly struggling to raise his head. Strapped in the chair, he was placed in a jail cell for more than two hours before an ambulance was called. He died shortly afterward at a Dallas hospital.

“Based on the information published in your article, we are going to secure and review the entire case file from the police agency and from any other sources,” Jason Hermus, the assistant district attorney who leads the office’s Public Integrity Division, said in an email. Depending on what prosecutors find, Hermus said the office could open a criminal investigation into the police officers’ conduct or take the case to a grand jury for possible indictments.

Robert and Kathy Dyer, who on the advice of their lawyer hadn’t viewed the videos, said they were pleased with the attention Graham’s story was getting. “We are in shock from what we have seen and read, but very grateful to the press for bringing Graham’s case into the light,” they said in a written statement.

Hermus said the Dallas County district attorney’s office had recently changed its policies for reviewing cases in which a person died in police custody to give prosecutors a more active role in investigations. Prior to 2015, the agency would make itself available to offer “input and advice,” but now prosecutors have a direct role in custodial death cases from the start, Hermus said.

“The new approach requires that representatives of the District Attorney’s Office be called out to the scene at the time of the incident, and further requires presentation of all investigative findings and live testimony of all fact witnesses to a Grand Jury,” he explained in an email. “The purpose behind the policy change was to ensure an independent, unbiased, and extremely thorough outside investigation on all (officer-involved shootings) and (death-in-custody) cases within our jurisdiction.”

Hermus added: “Because Graham Dyer’s case predated the approach we adopted in 2015, the DA’s Office did not respond to the incident at the time of its occurrence and the case was not investigated by our office. … After a thorough review of all of the facts and all of the evidence available, we will proceed to do whatever is right and just.”

The Dyers’ Fort Worth attorney said she welcomed the district attorney’s review. “We have hope that, after a long and agonizing road, this family may finally get some justice,” Susan Hutchison said.

Wayne Larson, a city of Mesquite spokesman, didn’t immediately respond to a request for comment.

Since their story has been published, Robert and Kathy Dyer have traveled to Austin, on Monday testifying in front of legislators contemplating a bill that would close the legal loophole that had kept Graham’s files secret. House Bill 3234 would compel police to turn over their records in cases in which the suspect dies.

On Wednesday, state Rep. Victoria Neave, a Dallas Democrat whose district includes Mesquite, said in a statement she supported changing the law.

“To learn the law was used to hide the truth from grieving parents only compounds that tragedy,” she said. “We should all take stock in the example of the Dyers, who have shown amazing strength to be able to set aside their pain of the tragic loss of their son, in order to help ensure no other parent will ever again suffer the injustices they have.”