As lawyers laid out their opening arguments in the trial of the man accused of gunning down Chicago Police Commander Paul Bauer, an attorney representing Shomari Legghette laid out a defense that stunned the courtroom.

Scott Kamin, who is representing Legghette in the case, argues that Bauer's death was a tragedy, but that his client was acting in self defense when he opened fire in a stairwell near the Thompson Center on the fateful day in Feb. 2018.

"It's a tragedy....but Commander Bauer brought it upon himself," Kamin said.

Kamin argued that his client had no idea that the man he was running from on the day of the shooting was Bauer. The police commander, hearing a radio call of a suspect fleeing police, jumped into action when he saw Legghette, and after a physical altercation that resulted in both men tumbling down a stairwell, Legghette allegedly pulled out a weapon and shot Bauer six times, killing him.

Kamin says that his client was "trying to sell drugs" when he was confronted by police, and that's why he was fleeing the scene.

The defense argued that Kamin was "cornered" in the stairwell by Bauer, and that he could not see Bauer's uniform at the time of the shooting.

Assistant State's Attorney Risa Lanier disputed the defense's account of events, saying that Legghette was an extremely dangerous man who was wearing body armor and was well-armed at the time of the incident.

Chicago police officers honor Commander Paul Bauer, who was gunned down in the line of duty while chasing a fleeing suspect two years ago.

"He was wearing body armor and a bulletproof vest, carrying packets of cocaine, heroin and marijuana," Lanier said. "He was armed with a long metal stake. He was also armed with a 9MM Glock, a semi-automatic handgun with an extended magazine."

The prosecution argues that the shooting was not "self-defense," as the defendant claims, but that it was an execution.

"He knew that Paul Bauer was a police officer...a police officer attempting to detain him, and he killed him for it," Lanier said.

Legghette's lawyer says that his client was wearing the body armor for protection.

"He gets shot at a lot," he argued. "He wears body armor to protect himself. It's that simple."

Before opening arguments began Tuesday, a pair of motions made by defense attorneys were denied, including a motion to dismiss the case because of the “lack of a speedy trial” and a motion to change venue because of the publicity the case had generated.

The trial is expected to take approximately a week and a half, and Legghette is expected to take the stand in his own defense.

He faces charges of first degree murder, armed violence and weapons charges in the case.