It comes more than a week after a JPSO deputy shot and killed a suspect.
Sheriff Joe Lopinto said that's when Reyes allegedly pointed a gun at the cops, and one of them shot him dead. Investigators say they recovered two guns and drugs on his person.
Video from another deputy's TASER reportedly showed the gun in Reyes' hand when he died.
His family has said publicly that they do not believe he would have pointed that gun at the police.
That rally is expected to march from JPSO to the Gretna Courthouse.
Businesses in the area have been closing early and sending employees home over worries there may be vandalism and violence.