Wednesday marked the start of the trial for the sole Louisville, Kentucky, police officer charged in connection to the “no-knock” search warrant raid that killed Breonna Taylor.

Brett Hankison is charged with three counts of first-degree wanton endangerment of Taylor’s neighbors. He allegedly fired shots that endangered three people who were inside an apartment directly behind Taylor’s. He will testify at the trial.

Hankison was fired from the Louisville Police Department after the March 2020 shooting and is the only officer charged in connection with the incident. No officers have been charged with shooting Taylor.

The deadly shooting took place shortly after midnight on March 13, 2020. Taylor, a 26-year-old Black medical worker, was asleep at home with her boyfriend, Kenneth Walker.

Officers arrived and executed a “no-knock” search warrant as part of an investigation into a suspected drug operation, allegedly linked to Taylor’s ex-boyfriend.

Walker, who claims he thought the officers were intruders, fired one shot from his handgun, striking an officer in the leg. In response, police opened fire, and Taylor was shot multiple times. No drugs were found in Taylor’s apartment.

In opening statements Wednesday, Assistant Attorney General Barbara Whaley explained that this case isn’t about the Louisville Metro Police Department the search warrant, but about Taylor’s neighbors: Cody Etherton, his wife Chelsey Napper and their 5-year-old son. Whaley said that Hankison fired five bullets into Taylor’s apartment, three of which reached Etherton’s apartment.

Whaley said when officers breached Taylor’s apartment, the officer who fatally shot Taylor moved up to cover the officer with the battering ram, putting himself in the line of fire. Hankison was supposed to be in this role but was telling a person who was leaving a neighboring apartment to go back inside, Whaley said.

Whaley said Hankison had been engaging with that person when shots rang out. She said Hankison fired perpendicular to where the shot came from inside of Taylor’s apartment.

The prosecutor said Etherton jumped up when he heard the ram at Taylor’s apartment and walked toward his front door to see what was going on.

“A bullet whizzed close to his head that he heard, and then saw debris, drywall dust, where that bullet had come through,” Whaley said.

He crawled back to his bedroom and then went back to the front bedroom to retrieve his 5-year-old son, she said.

Whaley also said that Hankison gave a statement to investigators claiming he saw a shooter with an AR-15-style rifle in a combat position. No AR-15-style rifle was recovered from Taylor’s apartment, Whaley said.

Hankison’s defense attorney, Stew Matthews, said in his opening statement that he didn’t plan to dispute the evidence presented by the prosecution, but the “issue is what was the reasoning behind his [Hankison] firing the shots.”

Matthews focused on the chaos of the situation and said that Hankison will testify.

Matthews said the prosecution doesn’t know whether or not Hankison could see what was going on into the doorway and that it was “not accurate” to say that he couldn’t see into the hallway when the door was breached.

Matthews said that Hankison saw the muzzle flash from the gun that was fired at officers and that “his perception of it was that it was an AR-15 rifle.”

Matthews said that when Hankison fired his gun, he was “attempting to defend and save the lives of his brother officers.” He said that under the operating procedures of the police department, officers are obligated to defend other officers and citizens, and “that’s exactly what Brett Hankison was doing in this situation.”

“His actions were reasonable and justified given the chaotic situation he was in,” Matthews said.

Hankison has pleaded not guilty. If convicted, he faces up to five years in prison.

Two other officers involved were also fired from the police department: the officer who fired the shot that killed Taylor per a ballistics analysis and the officer who prepared the search warrant.

ABC News’ Kiara Alfonseca contributed to this report.