Follow this link to read the transcript of our chat on American assassins with Bill Dedman, investigative reporter for msnbc.com.

If you like, you can also add your comments on that page as well.

Myths about assassins are commonplace. They're loners, the myth goes. They're crazy, deranged, anarchists.

Yesterday in The New York Times, columnist David Brooks wrote about Jared Loughner, who is accused in the Tucson shooting of a federal judge, congresswoman and others:

"Other themes from Loughner's life fit the rampage-killer profile."

The problem is, there is no profile. And they're not rampage killers. (Bulls go on rampages. Assassins plan.)

A thorough study of assassins was published by the United States Secret Service in 1998, and it debunked many of these myths. The Secret Service studied 83 people who killed a public official or celebrity, or who made an attempt, or approached with a weapon and were caught.

What have researchers learned from studying previous assassinations and attempts to kill politicians and public figures in America? Is there a profile? What are the types of people who do this? Have they been mentally ill? Drug users? Suicidal? What are their motivations or grievances? Have they been political? Members of radical groups? What steps do they take to plan? Do they tell others? How do they choose their targets? Do they make threats?

Bill Dedman has written about this issue for more than a decade, first when the Secret Service completed its study of assassins and attempted assassins. He has interviewed the researchers, and written about their later work on school shootings.