Gray attended Aledo High School in Aledo, Texas, where he broke the all-time high school touchdown record with 205 eclipsing Mike Hart's record of 204 touchdowns.[4][5] As a junior, he rushed for 323 yards and eight touchdowns in the Texas Class 4A Division II championship game against La Marque High School on December 17 at Cowboys Stadium, which gave him a total of 59 rushing touchdowns for the 2010 high school football season and surpassed Kenneth Hall's single-season record of 57 set in 1953.[2] Gray had rushed for 252 yards and four touchdowns in the 2009 state championship victory over Brenham High School.[2] In 2011, Gray led Aledo to its third straight state championship with 241 rushing yards.[6] Along the way, he scored his 205th touchdown establishing the national high school career record.[4] He finished his high school career first all-time in touchdowns and second all-time in points scored.[7]
Gray was also on the school's track & field team, where he competed as a sprinter. He was a 3 time district champion in the 100-meter dash. As a junior in 2009, he won the 100 meters at the 4th Johnny Perkins Pirate Relays, with a career-best time of 10.58 seconds.[9] He also competed in the 200 meters, placing fifth at the 2009 Elk Relays.[10]
Gray tore his right Achilles tendon in 2013, and his left Achilles in 2015.[11] The tendon tears put Gray's career on hold, and Gray went undrafted in the 2016 NFL draft.[12]
Several NFL teams showed interest in Gray as a free agent following the draft.[13] In 2017, after demonstrating a 4.5-second 40-yard dash and a 36-inch vertical leap at the annual Texas Pro Day workout, Gray landed a tryout with the New York Giants.[14] After attending the Giants' rookie camp, Gray received invites to rookie camps for the Calgary Stampeders, Winnipeg Blue Bombers and Saskatchewan Roughriders of the Canadian Football League; however, Gray ultimately never played for any of them.[15]
On April 8, 2021, the Frisco Fighters announced that they had signed Gray for the 2021 season.[16]