DALLAS (CBSDFW.COM/AP) — The family of an unarmed black man who was shot and killed in his own apartment by a white former Dallas police officer filed a federal lawsuit on Friday.

The suit argues that Amber Guyger used excessive force when she gunned down Botham Jean, a 26-year-old native of St. Lucia, inside his apartment on Sept. 6. According to court records, Guyger reported she mistook his apartment for her own and thought she’d encountered an intruder.

police officer Botham Jeans Family Files Suit Against Former Dallas Officer

Dallas police officer Amber Guyger stands charged with manslaughter in the fatal shooting of Botham Shem Jean who she mistakenly thought was in her apartment.

Guyger and the city of Dallas are named as defendants in the lawsuit. Jean’s parents, Bertrum Jean and Allison Jean, are listed as plaintiffs.

Guyger was arrested and charged with manslaughter days after the shooting and has since been fired from the Dallas Police Department. The lawsuit contends the department did not adequately train Guyger, who had ended her shift prior to the shooting.

The litigation argues Guyger was acting under her scope as a Dallas officer during the deadly encounter.

“Officer Guyger was ill-trained, and as a result, defaulted to the defective DPD policy: to use deadly force even when there exist no immediate threat of harm to themselves or others,” the lawsuit said.

There remains conflicting narratives over what led up to the deadly shooting.

An affidavit prepared by the Texas Rangers said Guyger went to the wrong apartment after ending her shift on Sept. 6. The door, according to the document, was ajar and Guyger opened it.

Inside, the lights were off and a figure in the darkness that cast a large silhouette across the room, according to Guyger. She said she thought her apartment was being burglarized and gave verbal commands to the person, who ignored them.

She then pulled out her firearm and shot two times, hitting Jean once in the torso, according to the affidavit. The lawsuit said Guyger did not give emergency aid to Jean following the gunfire.

Lee Merritt, one of the attorneys for Jean’s family, cast doubt on Guyger’s narrative. Merritt has said that two independent witnesses told him they heard knocking on the door in the hallway before the shooting.

He said one witness reported hearing a woman’s voice saying, “Let me in! Let me in!”

“We wanted to create a lawsuit that not only dealt with this incident as an isolated incident but really the policies and procedures by the City of Dallas that allowed this kind of thing to happen,” said Merritt. “We decided that we would focus this lawsuit on dealing with the policy makers – the mayor, the city council,  the police chief – who are responsible for training those officers who are responsible for disciplining those who are engaged in misconduct”

Dallas police on Friday declined to comment on the litigation, as did Guyger’s criminal attorney Robert Rogers.

Jean was not the first person shot by the former officer.

Gugyer shot and wounded Uvaldo Perez, on May 12, 2017, while she was on duty. An affidavit in the case filed against Perez said police were looking for a suspect when Guyger and another officer were called to assist a third. Perez got out of a car and became combative with Guyger and another officer.

A struggle started and she opened fire after Perez wrestled her Taser away from her.

According to the lawsuit filed Friday, Guyger was not required to receive any mental counseling following the 2017 shooting, in which she was not charged.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)