With the simplest of motives — breaking up the boredom of an Oklahoma summer — three teenagers followed an Australian collegiate baseball player who was attending school in the U.S. and killed him with a shot to the back for "the fun of it," prosecutors said Tuesday as they charged two of the teens with murder.

As the boys appeared in an Oklahoma courtroom, a 17-year-old blurted out, "I pulled the trigger," then wept after a judge told him that Tuesday's hearing wasn't the time or place to sort out the facts of the case.

Prosecutor Jason Hicks called the boys "thugs" as he told Stephens County Judge Jerry Herberger how Christopher Lane, 22, of Melbourne, died on a city street.

Chancey Allen Luna, 16, and James Francis Edwards, Jr., 15, of Duncan were charged with first-degree murder and, under Oklahoma law, will be tried as adults. Michael Dewayne Jones, 17, of Duncan was accused of using a vehicle in the discharge of a weapon and accessory to first-degree murder after the fact. He is considered a young offender but will be tried in adult court.

"I'm appalled," Hicks said after the hearing. "This is not supposed to happen in this community."

Shot in the back

In court, Hicks said Luna was sitting in the rear seat of a car when he pulled the trigger on a .22 caliber revolver and shot Lane once in the back. Hicks said Jones was driving the vehicle and Edwards was in the passenger seat.

Lane, who had come to the U.S. to study and play baseball, was out for a jog in an Oklahoma neighbourhood when he was gunned down at random by three 'bored' teenagers who decided to kill someone for fun, police said. (Associated Press/Essendon Baseball Club)

Edwards has had run-ins with the law previously and had been in court Friday, the day of the killing, to sign documents related to his juvenile probation.

"I believe this man is a threat to the community and should not be let out," Hicks said as he requested no bond for Edwards. "He thinks it's all a joke."

The two younger boys were held without bond; Bond was set at $1 million US for Jones.

Family and friends on two continents mourned Lane, who gave up pursuit of an Australian football career to pursue his passion for baseball, an American pastime.

His girlfriend, Sarah Harper, tearfully laid a cross at a streetside memorial in Duncan while half a world away, an impromptu memorial grew at the home plate he protected as a catcher on his youth team.

"We just thought we'd leave it," Sarah Harper said as she visited the memorial on Duncan's north, well-to-do side. "This is his final spot."

Flowers, photos and an Australian flag already adorned the roadside in a tribute to Lane.

"I don't know anybody who's left this. It means a lot," Harper said.

Memorial game set for Sunday

Police Chief Dan Ford has said the boys wanted to overcome a boring end to their summer vacation — classes in Duncan resumed Tuesday — and that Jones told officers that they were bored and killed Lane for "the fun of it."

Lane played at East Central University in Ada, about 137 km east of Duncan, and had been visiting Harper and her parents after he and his girlfriend returned to the U.S. from Australia about a week ago.

His old team, Essendon, scheduled a memorial game for Sunday to raise funds for Lane's parents as they worked to have their boy's remains sent home.

At Essendon Catholic School, Lane will be remembered at a November mass in which all former students who have died are mourned and celebrated, former school captain David Ireland told The Age newspaper in Melbourne.

"He was the sort of guy at school who everyone knew and knew quite well," Ireland said of Lane. "He loved his footy (Australian football) and his sport and spent a lot of time with mates."

Melbourne's Herald Sun newspaper reported that roses and a baseball were placed Monday on the home plate where Lane played as a youth with the message, "A wonderful young man taken too soon. Why?"

Australian politician urges boycott of U.S.

Former deputy prime minister Tim Fischer criticized the National Rifle Association and asked Australians to avoid the U.S. as a way to force its Congress to act on gun control.

"Tourists thinking of going to the U.S.A. should think twice," Fischer told the Herald Sun.

"This is the bitter harvest and legacy of the policies of the NRA that even blocked background checks for people buying guns at gun shows. People should take this into account before going to the United States. 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 U.S.A. There is a gun for almost every American."

Tara Harper, Sarah Harper's cousin, said her family was working with the Lanes on funeral arrangements but that the girlfriend didn't want to attend court proceedings.

"She wants nothing to do with them. She doesn't want to see them. She doesn't want to hear them," Tara Harper said. "I don't think we'll ever know why it happened. No answer will ever be satisfying, no matter what it is."

Brazen shooting 'unusual'

Police said they had been called to a home in Duncan's gritty east side in response to a possible shooting. At the home Tuesday, pieces of cement with the phrases "happiness lives in hearts that love" and "with God all things are possible" written on them sat cracked on the front porch.

One window was covered with foil, and cardboard and a satellite dish was perched on the roof. No one answered at the home or at homes next door or across the street.

At the site of the shooting, Bill Renfrow, 85, said he saw emergency workers tending to Lane and believed there had been a hit-and-run accident behind his home.

"It's very saddening. It's a terrible thing to happen. It's so unusual," he said, later adding: "He was a guest in the country."