Ronald Gasser was sentenced to 30 years in jail for the 2016 fatal shooting of former NFL running back Joe McKnight in Louisiana. He was convicted of manslaughter in January.
"This tragedy did not need to happen," Judge Ellen Shirer Kovach said.
Gasser's defense attorneys previously filed a motion requesting a new trial, which was denied by a judge.
His team also asked the judge for leniency because he is a decorated veteran of the U.S. Marine Corps.
McKnight was shot by Gasser at a Terrytown intersection on Dec. 1, 2016. Gasser argued that he shot McKnight in self-defense following a five-mile road rage chase.
McKnight played for USC before four seasons in the NFL with the New York Jets and Kansas City Chiefs.