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Duane Morrison, 53, has been identified as the gunman who took six girls hostage in a high school classroom, killing one. ((Jefferson County Sheriff's Office/Associated Press))

A gunman who took six girls hostage at a Colorado high schoolandthen killed one teenager as well as himself sexually assaulted some of them, a U.S. law enforcement officer said Thursday.

"He did traumatize and assault our children," Park County Sheriff Fred Wegener told the Associated Press a day after the hostage-taking. "I'll only say that it's sexual in nature."

Police have identified the gunman as Duane R. Morrison, 53, of the Denver area.

Theysaid he lived out of his vehicle and had no known connections to the area, the hostages or the school in Bailey, which is about 50 kilometres from Littleton, Colo., where two students shot and killed 13 peopleat Columbine High School in 1999.

According to a witness,Morrison wanted onlyfemale studentsand forced the male students to leave the second-floor classroom at PlatteCanyon High School on Wednesday afternoon in the small town of Bailey, about 55 kilometres southwest of Denver.

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Members of a SWAT team exit Platte Canyon High School in Bailey, Colo., during Wednesday's hostage-taking. ((Dennis Schroeder, Rocky Mountain News/Associated Press))

Morrison killed one of the hostages before he turned the gun on himself as a SWAT team charged the room where he was cornered.Another girl escaped.

Friends have identified the victim as Emily Keyes, 16. They said she was a sweet girl who played volleyball, was a member of the high school debating team and worked at a local restaurant.

Police said they had no motive yet for the hostage-taking.

Separated males from females

It began when Morrison walked into the building, opened fire and claimed to have explosives. He separated the males from the females and held six of the girls. A young girl was released shortly after, then hours later, three others were allowed to leave.

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Paramedics transport a shooting victim out of Platte Canyon High School during the hostage standoff that resulted in the death of one student, and the gunman killing himself. ((Marc Piscotty, The Rocky Mountain News/Associated Press))

Wegener said authorities decided to enter the school to save the two remaining hostages after Morrison cut off negotiations and set a deadline. He said authorities used explosives as they entered the classroom, only to have the suspect fire at officers, shoot one of the girls and then himself.

"My decision was to either wait, with the possibility of having two dead hostages, or act to try and save what I feared he would do to them," the sheriff said.

Cassidy Grigg, 16, a student at the school, said the gunman walked in, fired one shot at the floor and ordered the students to line up. He told the boys to leave and the girls to stay.

"You could tell that he wanted the females," Cassidy told NBC's Today show on Thursday. "He tapped me on the shoulder and he told me to leave the room. I told him, 'I don't want to leave."'

Grigg said the gunman told him that if he refused to leave, he would kill him.The studentsaid he wanted to stay to give support to the girls in the classroom.

School authoritieshave cancelledclasses at the school and its adjoining middle school for the rest of the week.

"This is something that has changed my school, changed my community," Wegener said. "My small county's gone."

With files from the Associated Press