As the shooting began Mr Sanders was heard screaming at his students to hit the floor.

Pupils say he stayed upright, risking his own body in the line of fire to make sure panicked students were clear of danger before he was hit twice in the chest by gunshots.

"He saved my life,'' student Candice Cushman told the local Denver Post.

"Then there was this kid who got shot in the leg" she told the paper. "Mr Sanders dragged him to the side so he wouldn't be shot again.

'We'll never see him again'

Terrified students were trapped for more than three hours

"He was the one jumping over the kids, getting people out of the way. Now we'll never see him again.''

Upstairs in the science block, student Steve Broden who was in the middle of biology study recalled seeing Mr Sanders burst through the door yelling at them to take cover.

"He came in with two shots in his back," he said. "He just came in and fell on his face and busted a bunch of teeth."

Four or five other teachers quickly followed, bringing their classes in to the room.

Popular coach

Badly wounded and coughing blood, Mr Sanders, who was also a popular sports coach at the school, was tended by students for more than three hours before police SWAT teams were able to lead them from the building.

One teacher reportedly spent hours on a mobile phone, receiving advice on care for the wounded teacher.

Marjorie Lindolim, 16, one of those who cared for the dying teacher, recalled how students had used makeshift bandages made of T-shirts to try to staunch the bleeding.

"He kept saying, `I can't breathe' and `I'm not going to make it,"' she told reporters.

With the shooting still continuing, students gently took out Mr Sanders' wallet so that he could see the pictures of his wife and daughters.

"Tell my girls I love them," the students recalled him saying.

As news of his death spread round an already traumatised school community, fellow sports coach Rick Bath paid tribute to a dedicated teacher.