He played college football at Appalachian State University.
He accepted a football scholarship from Appalachian State University, where he started at cornerback.
[1] Armstrong was signed as an undrafted free agent by the Dallas Cowboys after the 1987 NFL draft.
[2] After the NFLPA strike was declared on the third week of the 1987 season, those contests were canceled (reducing the 16-game season to 15) and the NFL decided that the games would be played with replacement players.
On September 22, 1987, he was re-signed to be a part of the Dallas replacement team that was given the mock name "Rhinestone Cowboys" by the media.