On January 2, Jose Nieves, 38, was shot and killed by an off-duty Chicago police officer in the Hermosa neighborhood after a verbal argument. 

Police spokesman Anthony Guglielmi confirmed that Nieves was unarmed when the shooting occurred.

"The person who was shot did not have a weapon. That much we know. The officer's weapon is the only one we found," he said.

According to the Chicago Tribune, the off-duty cop that killed Nieves is identified in court papers as Lowell Houser, a "28-year department veteran assigned to the public transportation unit." Even though the 57-year-old cop was removed from his police authority, he will continue to be paid throughout the investigation.

Chicago police superintendent Eddie Johnson said Nieves and Houser knew each other from an alleged confrontation before the shooting.

Nieves' sister, Angelica Nieves, said the encounter between the two has been ongoing, as Nieves and Houser lived in the same building. "He would complain about the guy pulling out his gun at him, him coming home from work. More than once, he's called 911. They've gone to the apartment. They've gone there. They don't do nothing about it. He's an officer," she said.

“If you are an officer, and you are getting shot at, and your life is in danger, I understand. But if a person doesn’t have a weapon, it doesn’t give you the right to take out your weapon and shoot at that person. It does not," Angelica told CBS 2 News.

"The officer stalked, threatened and, ultimately, killed Jose Nieves," the family's attorney, Andrew Stroth, said in an interview.

The family is suing the Chicago police department for her Nieves' alleged wrongful death. 

On January 6, a spokesperson for the department said it had determined Houser was acting in a police capacity at the time of the shooting. Currently the case is being investigated by the city's Independent Police Review Authority. 

As reported by the Chicago Tribune, the lawsuit alleges that the CPD was informed of the victim being detained by the officer before the killing.

Nieves was shot several times and his death was ruled a homicide, according to autopsy results from the Cook County medical examiner’s office.

A memorial for Nieves was held on January 6.

He was known to family as "Cheo" and worked in construction and security.

As reported by the Chicago Tribune, he had been arrested several times, and had felony charges as well, but was not convicted of serious offenses in Cook County.

Houser has reportedly incurred at least 20 disciplinary investigations since the early 1990s.

Department records obtained by The Chicago Tribune show that the officer has been suspended multiple times.