Mr Dickson said the perpetrators of the brutal crime could not expect their actions to go unpunished before the courts and praised the quick and effective police work which led to the arrests.
David Black (52) was attacked on the M1 motorway in County Armagh as he drove to work on Thursday, when a car pulled up beside his vehicle and fired a number of shots, forcing his car to veer into a ditch.
Stewart Dickson MLA said: “The brutal murder of David Black was a sickening ambush by those intent on dragging Northern Ireland back into the past.
“Effective investigative work by the PSNI has led to these quick arrests, proving there will be consequences for actions taken against society.
“Communities across Northern Ireland are united in their condemnation and disgust at this attack, together showing those who set out to disrupt our society that there is no place for this type of brutality in Northern Ireland.
“A family has been left devastated and I would urge anyone with information to come forward and assist the PSNI as they continue their investigation.”