Jackson Sr. said it was an amicable parting -- one initiated by the player.
"They just came to a mutual agreement," Jackson Sr. said. "There were no hard feelings. Coach Callahan expressed that he didn't want to see Leon go, but that he wanted what was best for him."
Callahan, in a prepared statement, confirmed that Jackson left "of his own volition."
"We appreciate the contributions he has made to this football program, and we wish him the best in the future."
Jackson, a 6-foot-1, 210-pound native of Pasco, Wash., will look at several schools, but Oregon State and Oregon top his list, Jackson Sr. said.
Leon would make a great addition to the team, but we must be cautious in getting him. He's appeared to have some academic issues at Nebraska and has a family to support.
Also, QB Allen Evridge has left Kansas State, and Oregon State is on his list.
Evridge told new coach Ron Prince of his intentions Tuesday and was granted a release from his scholarship. A formal announcement came Wednesday, making Evridge the third Wildcats quarterback to depart Manhattan since the spring game in April.
"Allan Evridge had a great start to his Kansas State career last season and we would have liked him to stay and be a part of this organization," Prince said in a statement. "We were looking forward to his contributions, but we understand that quarterbacks are competitive people by nature and we wish him well in his pursuit of his athletic and academic goals."
Evridge played in nine games as a redshirt freshman last season -- starting six -- and threw for a Kansas State freshman record 1,365 yards and six touchdowns. Against Texas A&M, he completed 23 of 44 passes for 357 yards and three touchdowns.
Evridge, meanwhile, seeks a new beginning. Since getting his release Wednesday, several schools have inquired about him, his father said. They include Wisconsin, TCU, Oregon State and New Mexico.