Remembering Columbine

A couple sit by the memorial at Chapel Hill Memorial Gardens for the teacher and 12 students who were killed at Columbine High School near Littleton, Colo., on Monday, April 20, 2009. A number of the people who were killed in the massacre at Columbine are buried at the cemetery.

Thirteen people lay down to symbolize those killed in the Columbine school shooting at a Columbine Remembrance and Rededication on the 10th anniversary of the Columbine attack, at the Capitol in Denver, on Monday, April 20, 2009.

Tom Mauser, father of slain student Daniel Mauser, speaks at the Columbine Remembrance and Rededication to mark the 10th anniversary of the Columbine school shooting at the Capitol in Denver, on Sunday, April 20, 2009. In front of him are 13 lilies, one for each person slain in the shooting.

Tom Mauser, father of slain student Daniel Mauser, speaks at the Columbine Remembrance and Rededication to mark the 10th anniversary of the Columbine school shooting at the Capitol in Denver, on Monday, April 20, 2009.

Tom Mauser, father of slain student Daniel Mauser, lays his hand on Elizabeth Wright, 20, as 13 persons lay down to symbolize those killed in the Columbine school shooting during the Columbine Remembrance and Rededication ceremony on the 10th anniversary of the attack at the Capitol building in Denver, Colo., on Monday, April 20, 2009.

A woman visits the grave site of Columbine High School student Rachael Scott at Chapel Hill Memorial Gardens near Littleton, Colo., on Monday, April 20, 2009, the 10th anniversary of the shooting at Columbine High School. Rachael Scott and eleven other students and teacher Dave Sanders were killed at the school.

Cassie Sadusky, 25, left, and her sister Jetta, 22, visit the grave sites of Columbine students Corey DePooter and Rachael Scott at Chapel Hill Memorial Gardens near Littleton, Colo., on Monday, April 20, 2009. The sisters were classmates of the 12 students and teacher that were killed at Columbine High School 10 years ago.

Columbine High School graduates Emily Honeycutt, 27, left, and Alison Remay, 27, place flowers on memorials for the teacher and 12 students that were killed in the Columbine High School massacre 10 years ago at Chapel Hill Memorial Gardens near Littleton, Colo., on Monday, April 20, 2009. Honeycutt and Remay were juniors at the school during the shooting and graduated the next year.

Elizabeth Hickman, right, hugs her daughter Maggie Hickman, left, both of Tennessee, at a candlelight vigil at the Columbine Memorial at Clement Park near Littleton, Colo., on Sunday, April 19, 2009.

Jen Beaver, 23, holds her candle as she watches the candlelight vigil at the Columbine Memorial at Clement Park near Littleton, Colo., on Sunday, April 19, 2009.

The family of slain school teacher Dave Sanders gathers at his memorial plaque for a candlelight vigil at the Columbine High School Memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009 on the eve of the 10th anniversary of the massacre.

Julia Bernzott, left, niece of Dave Sanders, Mallory Sanders, grand-daughter, Cindy Thirouin, daughter, Tiffany Strole, grand-daughter, and Coni Sanders, daughter of Dave Sanders stand with their candles at a vigil at the Columbine Memorial at Clement Park near Littleton, Colo., on Sunday, April 19, 2009. Dave Sanders was a science teacher who was killed with 12 students at the shooting at the school 10 years ago.

Columbine High School Principal Frank DeAngelis at a candlelight vigil at the Columbine Memorial at Clement Park near Littleton, Colo., on Sunday, April 19, 2009. DeAngelis was the principal at the time of the attack.

Lindsay Abrams, center, and her husband Danny Abrams, right, hold candles during a candlelight vigil at the Columbine Memorial at Clement Park near Littleton, Colo., on Sunday, April 19, 2009. Abrams is a former Columbine student and was a sophomore at the time of the attack.

Family and friends gather at a candlelight vigil at the Columbine High School memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009. Monday marks the 10th anniversary of the shooting at the school where a teacher and 12 students were killed.

Coni Sanders, left, and Cindy Thirouin, step-daughters of slain teacher Dave Sanders, attend a candlelight vigil at the Columbine High School memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009. Sanders and twelve students were killed at Columbine High School 10 years ago.

Family and friends gather for a candlelight vigil at the Columbine High School memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009. Monday is the 10th anniversary of the shooting at the school where a teacher and 12 students were killed.

Wade Abram and his 5-year-old daughter Mimi visit the Columbine High School memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009 prior to a candlelight vigil.

Brynn and David Gustafson read the inscriptions at the Columbine High School memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009, prior to a candlelight vigil on the eve of the 10th anniversary of the massacre.

Charles Russell, 25, of Dover, Del., reads the inscriptions at the Columbine High School Memorial at Clement Park, near Littleton, Colo., on Sunday, April 19, 2009, prior to a candle light vigil. Monday is the 10th anniversary of the shooting at Columbine.