ATLANTA — The suspect in a bus hijacking that prompted a police chase in Georgia allegedly got into a fight with a passenger before fatally shooting him with the victim's own gun, authorities said.

The incident began at approximately 4:35 p.m. ET Tuesday in downtown Atlanta, when police responded to a report of gunfire on a Gwinnett County Transit bus and a "possible hostage situation," the Atlanta Police Department said.

"Upon the officers' arrival at the scene, the bus fled the location, and a pursuit ensued," the Atlanta Police Department said in a press release.

The suspect -- identified as 39-year-old Joseph Grier, of Stone Mountain -- allegedly got into an argument with a male passenger after boarding the bus in downtown Atlanta, according to the Georgia Bureau of Investigation. The two got into a fight when the passenger then pulled out a gun, GBI said.

Grier allegedly took the man's gun and "began threatening passengers with it," GBI said in a statement Wednesday.

"Grier then shot the passenger and ordered the bus driver to flee the scene while threatening passengers with the gun," GBI said.

The suspect held the bus driver at gunpoint during the hijacking, according to Atlanta Mayor Andre Dickens.

There were 17 people on the bus at the time, including the bus driver, according to Atlanta Police Chief Darin Schierbaum.

During the pursuit, police received a 911 call from a family member of an occupant of the bus "saying he was receiving text messages that there had been a hijacking and that individuals were being held hostage against their will," Schierbaum told reporters during a press briefing Tuesday evening.

Police then received another 911 call made from the bus, which remained open throughout the pursuit and provided information that helped "craft an end of this hostage situation," the chief said.

The ensuing pursuit spanned multiple jurisdictions, during which police attempted "various tactics" to stop the bus, police said. The bus hit several police vehicles during the pursuit, GBI said.

The vehicle was ultimately disabled in Stone Mountain in DeKalb County, approximately 16 miles northeast of where the incident began, police said.

A Georgia State Patrol trooper fired his patrol rifle into the engine compartment of the bus, causing it to malfunction and stop running, according to GBI.

Once the bus stopped, DeKalb County SWAT officers positioned a Bearcat armored vehicle "to prevent any avenues of escape," the DeKalb County Police Department said in a statement.

Grier was taken into custody without further incident, police said.

SWAT officers found the gunshot victim while clearing the bus, DeKalb County police said. Police identified the victim as Ernest Byrd, 58.

Grier is accused of "knowingly and intentionally" shooting the victim in the leg and causing his death, according to the arrest affidavit. He has been charged with murder, as well as 14 counts of aggravated assault, 14 counts of kidnapping, hijacking a motor vehicle, possession of a firearm during the commission of a felony and possession of a firearm by a convicted felon, police said Wednesday.

Fulton County District Attorney Fani Willis said her office is unable to prosecute the case because one of her employees was on the bus, according to a letter she sent Wednesday to the Prosecuting Attorneys Council of Georgia requesting substitute counsel.

Byrd's family said they are heartbroken by the "senseless act" and said more details are needed to "fully comprehend the nature of this tragedy."

"We are deeply saddened by the tragic loss of our beloved husband, father, friend, uncle and grandfather," his family said in a statement. "He was a man known for his unwavering dedication to resolving conflicts and protecting others."

No other injuries were reported in the incident.

The investigation remains ongoing, Atlanta police said. GBI said it is also investigating the use of force by the state trooper.

A shaken passenger on the hijacked bus said the ordeal was "traumatic" and she is "thankful to be alive."

"It was something that we'd never forget," Paulette Gilbert, 60, told Atlanta ABC affiliate WSB, adding that she has ridden the bus for many years without incident.

The bus shooting and hijacking occurred after a separate, unrelated incident gunfire broke out at a food court at a downtown Atlanta shopping center on Tuesday afternoon, officials said. Three people were injured, and an off-duty Atlanta police officer shot the armed suspect, police said.

The suspect in the bus hijacking boarded the bus near the shopping center but was not involved in that shooting, Schierbaum said. A "common theme" was that the suspects in both incidents are convicted felons, he said.

Grier spoke to reporters following the incident at the food court, as media outlets sought witness reactions to that shooting before police say he then hijacked the bus.

In an interview with The Associated Press, Grier said he was in "extreme mode" when he saw the food court shooter and that he had knives on him but "couldn't get a gun." He also said he is bipolar.

Grier is being held at the Fulton County Jail. It is unclear if he has an attorney who can speak on his behalf.

Dickens said Tuesday he believes mental health "is going to play a role" in the incidents but added, "You're talking about too many guns in the hands of individuals that should not have guns."

The mayor decried the spate of gun violence and said Tuesday's incidents "reflected a breakdown in the criminal justice system and our social structures on multiple levels."

"I am both sad and I am angry that individuals that were going about their daily lives -- those that were just taking a bus ride home and those that were there for lunch or late lunch or having a gathering -- they really should not have to suffer that kind of trauma," the mayor said Wednesday. "These are the types of senseless acts of violence that we are trying to prevent here. They hurt families, they hurt businesses, and they hurt our beloved communities."

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