He said the three youths followed Lane in Jones' 2003 Ford Focus after he ran past a home where they had gathered.
Luna shot him in the back with a .22-caliber revolver, the prosecutor said.
Two women stopped to help Lane. He was taken to a hospital where he later died.
Police used surveillance footage from a local business to identify a car thought to be involved in the shooting.
Police then located the teens in the vehicle after a caller reported that juveniles were at his house with guns.
According to a probable cause statement, Jones admitted to being involved in the shooting, but said he did not pull the trigger.
At almost the time of the killing, Edwards was scheduled to be at the courthouse to meet with the office of juvenile affairs to sign his terms of probation in an unrelated matter, Hicks said.
Hicks said Edwards was cold and callous throughout the investigation and when he was being processed into the Stephens County jail he danced at the booking desk.
“His demeanor was this whole thing was one big joke,” Hicks said. “He thinks it's funny.”
The case has drawn international media coverage and prompted condemnation in Australia where one national leader called on Australian tourists to boycott the U.S.
Former Australian Deputy Prime Minister Tim Fischer was quoted in the Melbourne Herald Sun newspaper as saying such a move would send a stern message about the need for tighter gun control.
“I am deeply angry about this because of the callous attitude of the three teenagers, (but) it's a sign of the proliferation of guns on the ground in the USA,” said Fischer, who helped lead gun control reforms in Australia in 1996.
The three teenagers are next scheduled to appear in court in October.
Lane is the second East Central University student to suffer a violent death in the last eight months.
In December, 18-year-old Gennaro Sanchez was kidnapped and killed by a fellow freshman at the Ada school. In that case, prosecutors are seeking the death penalty against Jerrod Murray, 18, of Asher. In an affidavit, an undersheriff wrote that Murray confessed to killing Sanchez to see how it would feel.
Ada is about 90 miles east of Duncan. Lane frequently visited Duncan, where his girlfriend lives.