BARABOO, Wis. — A Wisconsin teen told investigators he shot his high school principal three times "on purpose," according to a videotaped statement played in court Tuesday at his trial on homicide charges.

But when investigators asked the then-15-year-old Eric Hainstock whether he meant to kill John Klang on Sept. 29, 2006, he said, "No, I just freaked out." (VIDEO)

In the video, Hainstock attempts to explain the shooting, but then says, "I don't know. I wasn't thinking."

Prosecutors allege Hainstock, now 16, knew what he was doing when he brought a .22-caliber handgun and a shotgun to Weston High School.

Hainstock is charged with first-degree intentional homicide for fatally shooting Klang, 49, in a school hallway. He has pleaded not guilty and could be sentenced to life in prison if convicted.

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His attorneys concede Hainstock is guilty of causing Klang's death through reckless behavior, but say he never intended to kill his principal.

In the interview, Hainstock tells a Wisconsin Department of Justice agent he woke up on Sept. 29 "ticked off" at his classmates and at Klang.

Most of his classmates picked on him and called him a "fag," Hainstock said.

Although he told the agents that he complained about the teasing to his teachers and principal, nothing was ever done, he said.

He decided to take two loaded guns to school on the morning of the shooting. After eating breakfast and waiting for his parents to leave the house, he said, he used a screwdriver to pry open his father's gun cabinet and retrieve the guns.

He loaded them and drove to school in his grandfather's pickup truck.

Eric Hainstock told investigators he woke up 'ticked off' on the morning of the shooting.

When Hainstock arrived at school, he took out the guns, walked into the school and told everyone to back up, he said.

Then Klang approached him.

"He grabbed me and I pulled the trigger three times," Hainstock said. "I shot him in the leg, the side and I think I nicked him in the head ... I'm not sure."

Hainstock eventually gave investigators a more detailed description of the minutes before he shot Klang.

When the school's maintenance man took the shotgun away from him, Hainstock said, he pulled out the handgun, pointed it at Klang and ordered the principal to go to his office, he said.

"I was by the lockers and we were walking," Hainstock said. "[Klang] came around me, wrapped his arms around me and I shot him."

After the interview, Hainstock casually chatted with the detectives about how good the food was at the jail and said that he didn't want the police to notify his parents of his arrest.

Testimony is scheduled to resume Wednesday. The trial is being streamed live on Court TV Extra.