[1] Mitchell successfully ran in the 4 x 400 m relay qualifiers at the 2012 Olympic Games despite breaking his fibula during the race, and was later awarded a silver medal after the team's placement in the final.

At the 2012 Summer Olympics held in London, Mitchell ran the first leg of the heat for the 4x400 metres relay and revealed afterwards that he broke his left fibula at the 200m mark.

In September 2012, during a visit by Olympians and Paralympians to the White House, President Barack Obama called Mitchell's successful relay one of his favorite moments of the games.

[6] In July 2020, Mitchell was persuaded to try bobsleigh by United States Bobsled and Skeleton Federation CEO Aron McGuire to try the sport.

[6] Mitchell, as the push athlete, finished fifth alongside driver Frank Del Duca in the two-man event at the IBSF World Championships, which was the best American result since 2013.