Harmon was born in Monrovia, the capital of Liberia, on December 15, 1996, and moved to Palmyra, New Jersey, in the United States when he was four.

[2] A 4-star recruit, he originally committed to South Carolina to play college football, but decommitted and attended NC State instead, over offers from Indiana, Miami, North Carolina, Rutgers, and West Virginia, among others.

[14][15] In the Redskins' 2019 season opener against the Philadelphia Eagles, he had two receptions for 31 yards in his NFL debut.

[23][24] Harmon signed with the Philadelphia Stars of the United States Football League on March 21, 2023.

[29] He was released during roster cuts on August 27, 2024 before re-signing with the team's practice squad the next day.