Like Smith, Heaggan-Brown is African-American.
Smith family's attorney, David Owens, also announced that a civil lawsuit has been filed against the former officer and the city of Milwaukee, Wisc.
The fatal encounter transpired over 12 seconds from the time Heaggan-Brown got out of his vehicle to begin chasing Smith to when the fatal shot was sacked.
The fatal shooting sparked several days of rioting in Smith's predominantly black Milwaukee neighborhood.
Heaggan-Brown shot Smith in August of 2016 after the officer and his partner stopped Smith on the street, suspecting that he was involved in a drug deal.
The second and fatal shot was sacked after Smith tossed his gun and dropped to the ground.
Prosecutors said that Heaggan-Brown's first shot was reasonable, his second was not, as he no longer had any reason to fear for his life.
Family members of a black man who was shot to death by a former Milwaukee police officer stormed out of a courtroom after the officer was acquitted in the death.
The officer was sacked from the Milwaukee Police Department in October following unrelated sexual assault charges. Prosecutors contend Smith was defenseless when Heaggan-Brown shot him in the chest because Smith had thrown his gun over a fence.
"While Smith raises his gun upward, P.O. Heaggan-Brown discharges one shot from his service weapon at Smith and Smith falls to the ground on his back". Heaggan-Brown's acquittal came less than a week after a Minnesota officer, Jeronimo Yanez, was acquitted in the shooting death of a black motorist seconds after the motorist informed him he had a gun. Heaggan-Brown fired the second shot because he believed Smith was reaching for his waist, according to the complaint.
"Obviously, everyone recognizes there was a loss of life, and I don't think any officer would want to be put in that situation and to have to make those decisions that he did, but those decisions were made, and I think the jury properly evaluated them", Smith said. At that moment, Heaggan-Brown fired at him, hitting his right arm. Smith is shown approaching a chain-link fence with a gun in hand when he's shot the first time. The trial judge is also allowing jurors to consider two lesser charges: second-degree reckless homicide, and reckless use of a firearm. A police expert in the use of deadly force says on Monday that Heaggan-Brown, on trial for fatally shooting a black man after a foot chase "acted in accordance with his training".