CEDAR RAPIDS - One of the teenagers charged in an assault that left a boy with a broken jaw admitted his role in the attack to police and told them he had been "mad at the world," according to court documents.

Keenan Baker, 16, of Cedar Rapids, made a brief initial appearance Friday morning in Linn County District Court. He has been charged as an adult with one count of assault causing serious injury, a class D felony, in connection with the Aug. 21 incident that left three boys injured.

Linn County Attorney Jerry Vander Sanden said Thursday his office will ask that two other assault charges against Baker be waived to adult court to join the felony count.

A second boy accused in the attack, 15-year-old Tyress Martin, of Cedar Rapids, is charged in juvenile court with one count of assault causing serious injury and two counts of assault causing bodily injury. Prosecutors have filed a motion to have Martin tried as an adult, but a judge has not yet ruled.

According to witnesses and police, four boys were walking home from Washington High School on Aug. 21, when they were attacked by two other boys in front of 368 20th St. SE. According to one boys mother, one of the assailants yelled Get off my block, before her son was punched from behind.

One of the victims, 15-year-old Christian Meek, spent two nights in a hospital for a broken jaw and a severed nerve, his mother said. Another 15-year-old boy had his two front teeth knocked out, but doctors were able to replace them.

According to a criminal complaint, Baker "admitted to police the attack was done without justification or any provocation by the victims and that he was 'mad at the world.'"

Police have said at least some members of the two groups knew each other from their days at McKinley Middle School.District Associate Judge Casey Jones set Baker's bond at $10,000 cash or surety. He denied a motion from Baker's public defender to be set Baker free on pre-trial supervised release. A preliminary hearing in Baker's case was set for Sept. 10.