BROWNSTOWN, Ind. - A teenager who confessed to a series of highway shootings that killed a man in southern Indiana had been on a hunting trip with relatives but got into an argument and drove off in anger shortly before the attacks, a prosecutor said Wednesday. Zachariah Blanton, 17, appeared at a brief court hearing Wednesday morning where a judge set a Dec. 13 date for his trial on charges of murder, attempted murder and criminal recklessness. Blanton starred at the sidewalk as officers led him into the Jackson County Courthouse. He did not enter a plea. Police believe that after the hunting trip argument, Blanton drove to a nearby overpass outside Seymour early Sunday, aimed his rifle over the trunk of his vehicle and began shooting at trucks on Interstate 65 about 60 miles south of Indianapolis. One bullet killed a passenger in a pickup and another wounded a man. Two hours later, a tractor-trailer and unoccupied sport utility vehicle were hit by bullets about 100 miles to the north, close to the teenager's hometown of Gaston. "He said he in fact did do the shootings, however, only with the intention of relieving pressure," John Kelly, an Indiana State Police crime scene technician, testified Tuesday during a probable cause hearing. The teen apparently had been arguing with relatives over gutting a deer during a hunting trip about 20 miles south of Seymour, Jackson County Prosecutor Stephen Pierson said. When investigators questioned him Tuesday after receiving a tip that he might have been involved, his demeanor was "cooperative, it was remorseful," said Sheriff George Sheridan Jr. of Delaware County, where the second set of shootings occurred. Blanton came to the attention of investigators on Monday after an acquaintance told a Delaware County reserve deputy that the teen might be involved in the shootings, State Police Superintendent Paul Whitesell said. Pierson said police had recovered a rifle they believed was used in the shooting death of Jerry L. Ross, 40, of New Albany. Blanton had previous brushes with the law for what Sheridan would describe only as "crimes of sex and of theft." A message seeking comment from Blanton's grandparents, who police said were his legal guardians, was not returned. On the teen's Internet page on MySpace.com, he listed his interests as "Huntin, Fishin, Muddin and goin out with friends." Blanton's great-aunt Denise Blanton told The Star Press of Muncie that she was shocked by the allegations. "I can't imagine that he would be involved," she said. Kenneth Shipley, 59, a family friend who lives in Gaston, said he was also surprised. "This isn't the Zach I knew," he said. "I took this real hard. Zach just needed some attention, someone to talk to."