Killian attends Mountain Home High School where he plays both baseball and basketball. Killian is ranked nationally as the 100th best prospect in the class of 2012 by Perfect Game. Killian was selected to play in the Under Armour All-America Game at Wrigley Field and also participated in the Area Code Games, playing for the Chicago White Sox. Killian made the all-tournament team at the 2011 WWBA World Championship while playing with the Texas Scout Team Yankees.
"We feel that Trey is the top right-handed pitcher in the state of Arkansas," (Razorback head coach Dave Van) Horn said. "He drew some national attention this past year with his performance in high school. He's another player whose fastball sits in the low 90s with movement. He is another player that is being highly scouted by professional teams. He can come in and make a major impact as a freshman."