By M. Alex Johnson, Staff Writer, NBC News
A gunman opened fire at a high school in Colorado on Friday, wounding two fellow students before killing himself, authorities said.
One of the students was seriously wounded and was in surgery after the gunman shot the youth at Arapahoe High School in Centennial, Arapahoe County Sheriff Grayson Robinson said. He said initial reports that the student confronted the gunman turned out not to be true.
The second injured student was reported in good condition with a minor gunshot wound.
The shooter, a male student, said he was looking for a specific teacher by name when the incident began about 12:30 p.m. (2:30 p.m. ET), Robinson said.
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"The teacher exited the school immediately, which was, in my opinion, the most important tactical decision that could have been made," Robinson said. "It was a very good tactical decision to try to take the student with him."
An army of officers responded, having dramatically changed their standing orders after the deaths of 12 students and a teacher 14 years ago at Columbine High School — just about 10 miles away. Instead of waiting for backup, they rushed in immediately.
They found the shooter in a classroom about 20 minutes after they began their search, Robinson said. He said investigators knew his identity and were talking to his family.
Police, sheriff's deputies and agents of the U.S. Bureau of Alcohol, Firearms, Tobacco and Explosives obtained a search warrant and barreled into a home about 4 miles from the school, looking for any other possible weapons or clues.
No one appeared to be home, a neighbor said.
"An ATF agent said we should stay in the house," she told NBC station KUSA of Denver. "I didn't ask any questions."
'I was just freaking out'
"We heard gunshots — one, two, three — and we kind of looked at each other, and we knew it was real," said Jack Berning, a student at the school.
"There were more gunshots happening. They stopped, and I heard a woman screaming," he said, adding:
"I was just freaking out. I don't know."
Madison Berry, a senior at the school, said she had taken classes with the gunman.
"He was very outspoken — always involved with class discussion," she said. "So it was kind of odd to see that he was the one who did this."
"You would never expect this to happen at such a great school as Arapahoe," she added.
Parents were being asked to gather at nearby schools and churches, the sheriff's office said. They dropped whatever they were doing to rush to the scene — one was seen in full medical scrubs, as though he had just raced out of a doctor's office, KUSA reported.
A janitor first spotted the gunman and alerted authorities. The man, who said he wanted to be identified only as Fabian, said the gunman was running side to side, kind of military style."
I looked to see if there was a gun," Fabian told KUSA. "It was a shotgun."
"When he went into the library, he said, 'Where is Murphy?'" Fabian said.
Robinson confirmed that the gunman was armed with a shotgun.
'A traumatic situation'
Authorities said that while they had no indication of a second shooter, they proceeded as though there might have been one as a matter of caution. Students were led out of the building with their arms in the air, some of them being patted down by police.
"The kids have been through a traumatic situation," said Robinson, who was serving his last day as sheriff after having announced his retirement. "We need to ensure that anyone we evacuate isn't part of our problem. We're doing the evacuation slowly and deliberately."
President Barack Obama was briefed about the shooting, White House officials said.
Colorado Gov. John Hickenlooper called the incident "an unspeakable horror," telling reporters at a news briefing that "this is a good school district."
Arapahoe High School, with 2,000 students, is an affluent suburb of Denver in the same county where James Eagan Holmes is accused of having killed 12 people in a movie theater in the town of Aurora last year.
Tom Costello, Pete Williams, Azhar Fateh and Geoff Tofield contributed to this report.