Violent attacks on public officials, like the one that claimed the life of Colorado's executive director of the Department of Corrections, are on the rise in the United States, says at least one leading expert who tracks such incidents.

The motive behind the Colorado killing of Tom Clements wasn't immediately known, but the rate of such attacks has increased rapidly in the last three years in the United States, said Glenn McGovern, a senior investigator with the Santa Clara District Attorney's Office in California, who has tracked such attacks throughout the world since 1950.

McGovern said that from 2000 through 2009, there were 36 attacks against public officials in the United States, 12 of which he classifies as completed, meaning a weapon actually was fired or exploded.

He said that from 2010 through 2012, there were 35 such attacks in the United States, nine of which he said were completed. Through this year, there have been at least five such attacks in less than three months, he said.

Most of the attacks are occurring in residential areas, he added.

"I assume that is because everyone is hardening up their facilities," McGovern added. "If you're an aggressor, you understand that. Why not take them out where they're most vulnerable: their home."

Usually revenge is the motive, McGovern said. The incidents he has tracked include the 2008 fatal shooting of Adams County prosecutor Sean May outside his northwest Denver home. That killing remains unsolved.


Christopher N. Osher: 303-954-1747, cosher@denverpost.com or twitter.com/chrisosher