Ruppert was born on the 6th of January, 1938, in Hampton, Virginia, and he attended and graduated from Virginia State University. Shortly before graduating college, he enlisted in the US Army and after completing Officer Candidate School, he received his commission. Ruppert was a First Lieutenant when he deployed in support of the Vietnam War and it was his actions on the 15th of March, 1967, that would earn him the Medal of Honor. The citation reads:

For conspicuous gallantry and intrepidity in action at the risk of his life above and beyond the call of duty. While leading a platoon of Company B, 1st Lt. Sargent was investigating a reported Viet Cong meetinghouse and weapons cache. A tunnel entrance which 1st Lt. Sargent observed was booby-trapped. He tried to destroy the booby trap and blow the cover from the tunnel using hand grenades, but this attempt was not successful. He and his demolition man moved in to destroy the booby trap and cover which flushed a Viet Cong soldier from the tunnel, who was immediately killed by the nearby platoon sergeant. First Lt. Sargent, the platoon sergeant, and a forward observer moved toward the tunnel entrance. As they approached, another Viet Cong emerged and threw two hand grenades that landed in the midst of the group. First Lt. Sargent fired three shots at the enemy then turned and unhesitatingly threw himself over the two grenades. He was mortally wounded, and his two companions were lightly wounded when the grenades exploded. By his courageous and selfless act of exceptional heroism, he saved the lives of the platoon sergeant and forward observer and prevented the injury or death of several other nearby comrades. First Lt. Sargent's actions were in keeping with the highest traditions of the military service and reflect great credit upon himself and the U.S. Army.

Ruppert was 29 years old when died and his wife received his Medal of Honor in their home on the 20th of March, 1969, from General Donley Bolton. This made him the first black officer to receive the Medal of Honor and would be the only one until 1997 when three World War 2 recipients of the Distinguished Service Cross would have those awards upgraded. Ruppert Leon Sargent is buried in the Hampton National Cemetery in Hampton, Virginia: Section FI, Site 7596. His name appears on the Vietnam Veterans Memorial Wall: Panel 16E, Line 86.