O’Malley shot and killed a suspect in a carjacking in March. The swift decision to prosecute has prompted outrage by the police union and law enforcement officials.

O’Malley, 33, has pleaded not guilty to manslaughter for the death of Stephenson King, 39, who was shot March 11 while he allegedly tried to flee a traffic stop in a stolen car. Prosecutors determined that O’Malley had no justification for shooting at a moving vehicle.

“It is disappointing that the Suffolk County District Attorney’s Office is choosing to second-guess an officer whose only goal was to protect the public,” O’Malley’s lawyer, David Yannetti, said in an email to the Globe. “We will continue to vigorously defend this officer and this case.”

“The main issue in this case will be who the aggressor really was and whether Officer O’Malley acted in lawful defense,” Yannetti wrote in court filings.

On Wednesday, Yannetti filed several defense motions in the Roxbury division of Boston Municipal Court, in an effort to illustrate “King’s mayhem and reign of terror,” spanning nearly two decades and resulting in more than 17 criminal cases across Massachusetts, court records show.

Over the years, King has been charged with strangulation, assault and battery with a dangerous weapon, carjacking, breaking and entering, gun charges, and resisting arrest, according to court filings.

At the time of his death, King was free on bail for at least three separate felony cases, and had active warrants for his arrest, court records said.

O’Malley is seeking King’s mental health, criminal, and court records from all of his past cases, recordings from police body-worn and dash cameras, the medical examiner’s file on King, along with statements taken from O’Malley and witnesses at the scene of the shooting.

O’Malley told investigators that when he shot King he feared for his own life and for the life of another office on the scene, believing his colleague was about to be run over.

Police had pursued King after he allegedly committed a carjacking outside a pizza restaurant in Boston’s Mission Hill neighborhood. About 15 minutes later, officers stopped the stolen car less than a mile away, at Linwood Square in Roxbury.

The driver ignored “multiple verbal commands” as officers approached and tried to drive away, police said.

King opened the car window, but did not turn the vehicle off. O’Malley drew his Taser and shouted, “Bro, I’m going to [expletive] shoot you,” the police report said.

That’s when King backed into the cruiser behind him, then maneuvered the vehicle forward and back “in an attempt to escape the police,” according to the report.

As King started to drive forward again, O’Malley fired three shots through the driver’s window, striking King, the report said.

King’s family has contended that he was experiencing a mental health crisis in the hours leading up to the deadly encounter.

In court filings, O’Malley’s lawyer, Yannetti, said King gave “O’Malley no choice that night.”

“Any suggestion that this shooting was precipitated by simply a ‘mental health crisis’ completely misses the point,” Yannetti wrote. “When facing an extremely dangerous threat, there is no time for a police officer to hold a counseling session on the street or to sit down to discuss the feelings of a menace who is intent on using a motor vehicle as a deadly weapon.”

“If a man is going to assault and carjack an innocent woman then threaten the lives and safety of the public and a police officer, that man needs to be stopped — whether he is in his right mind or not,” according to O’Malley’s motion.

O”Malley’s next court date, a probable-cause hearing, is scheduled for May 21.

Tonya Alanez can be reached at tonya.alanez@globe.com. Follow her @talanez.