An unarmed man was shot and killed by an off-duty police officer in Chicago on Monday morning. The incident was allegedly the result of a verbal altercation between two men, who had already been aware of each other from a confrontation roughly a week ago, Chicago Police Superintendent Eddie Johnson said at a press conference Monday.

The family of the victim identified him as 38-year-old Jose Nieves. Authorities later determined Nieves did not have a weapon during and instead only found the weapon of the off-duty officer. The police officer who fired the fatal shot was revealed to be a 57-year-old veteran of the mass transit unit. 

Angel Nieves, the victim’s father, told local reporters that the incident was “murder.” His son was shot several times.

Other family members told law enforcement that the deadly incident occurred in front of a residence around 9:14 a.m. local time when Nieves was with his girlfriend, according to the Chicago Sun Times. The off-duty police officer lived in the same apartment building as Nieves, where the two’s tumultuous history with one another had been on full display weeks leading up to the event, they said.

"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," the victim's sister Angelica Nieves told local reporters.

Angelica pointed to the facts that Nieves had been shot in the stomach, lower body, and back, which could indicate that Nieves was turned around when he was shot and killed.

Nieves’s cousin, Ada Chaparro, told local reporters that the killing "did not make sense." Chaparro, who lives nearby where the incident took place, said Nieves was a construction worker and also had a second job as a security guard at a local nightclub. He described his relative as a man who “didn’t like drama."

The officer was placed on administrative desk duty for the remainder of the investigation. He has been receiving medical treatment at a local hospital from injuries he suffered during the altercation.

Johnson said that more information would be revealed after receiving a brief from the police department and an Independent Police Review Authority on Tuesday. Police had been combing through surveillance video from the area sounding the crime scene and attempting to locate witnesses since Monday. The event took place on the same block as a local high school.

Monday’s deadly incident was already the second police-related shooting that prompted Chicago authorities to launch an investigation in 2017. A man in his 40’s was in a local hospital in serious condition over Chicago’s first police shooting of 2017 after he was shot following a car chase on Sunday.

President-elect Donald Trump took to Twitter Monday morning to voice his opinion about the violence that marred Chicago in 2016. The federal government should allocate more of its resources to better police a city that saw more homicides than Los Angeles and New York City combined, he said. Chicago witnessed more than 762 homicides and at least 4,300 shootings in 2016. It had not seen a year with more than 700 reported homicides since 1998, when there were 704, according to a Chicago Tribune report. Police attributed the uptick in murder in 2016 to the ongoing gang-violence occurring in predominately five neighborhoods throughout the city, the New York Daily News reported.