At Colorado high school not far from Columbine, the first reports came in around noon, reports CBS News correspondent Cynthia Bowers: A middle-aged man armed with a handgun had stormed the high school and taken six female students hostage in a classroom.
The student, Emily Keyes, 16, died from a gunshot wound in the head later at a hospital.
"It's hitting close to home because this is where Columbine occurred," said Jacki Kelley, a spokeswoman for the Jefferson County sheriff's office, which handled the 1999 shootings.
Some of the female hostages reportedly were sexually assaulted, reports CBS News correspondent Lee Frank.
During tense negotiations, the gunman released four of the hostages one by one but also told authorities his backpack contained a bomb and something would happen at 4 o'clock.
"He broke off negotiations and he wouldn't talk any more," said Sheriff Fred Wegener.
The decision was made to storm the building.
"Officers breached the classroom with explosives. Within seconds the suspect shot at entering swat officers, then shot one of the two female hostages, then shot himself," Wegener said.
Investigators Thursday morning still didn't know much about the gunman. There are reports he once lived in Bailey, and may have recently moved to Denver.
Many of the first responders at Platte Canyon were also the first on the scene six years ago at Columbine. Law enforcement in this tiny mountain town refuse to discuss a motive but say although they'd trained for this kind of thing they never expect it to play out in their tight-knit community.
"I was just praying that we would do the right thing," said Wegener.
Platte Canyon High School is about 40 miles, or an hour's drive, from Columbine.
When the gunman came into the classroom, one of the male students, Cassidy Grigg, asked to remain with the girls but the man would not allow it.