Columbine anniversary a day of sadness, fear

The people of Colorado paused Thursday to remember the victims of the worst school shooting in U.S. history, with solemn ceremonies and promises.

Exactly one year ago, two teenagers went on a rampage at Columbine High School, killing 12 students and a teacher before committing suicide.

A private memorial was held at the Denver-area school. But many students, still haunted by the memories of the killings, were not there.

"Although we will never forget, we will move forward," said the school's principal, who slowly read out the names of all the victims.

Flags flew at half staff throughout the state. A moment of silence was observed at 11:21 a.m. MDT, the time the attack began.

Fears of copycat violence in the U.S. and Canada prompted some schools to take dramatic security measures.

Rumours of a plot to kill students and teachers at Fredericton High, Canada's largest high school, kept most of the students at home Thursday.

Some schools in Toronto brought in extra security. Toronto police have investigated at least three threats in the days leading up to the Columbine anniversary.

In the United States, critics say the tragedy at Columbine has done nothing to strengthen gun control laws.