Larry Mackey, who was the lead federal prosecutor in the trials of McVeigh and Terry Nichols, is now retired from the Department of Justice and works at the Barnes and Thornburg law firm in Indianapolis.

He told 6News' Renee Jameson that he believes there is a lot of distrust and dissent in the country today, much like in 1995 when the federal building was bombed.

"A lot of law enforcement will tell you that militia is not really where you have to be worried. You have to be worried about Tim McVeigh, a trained Army veteran," Mackey said. "He knew what he needed to do when it came to explosives. Had a plan and executed it."

Mackey said what struck him about McVeigh during the 1997 trials is how stoic he was during the emotional testimony.

"When McVeigh sat in the courtroom and listened to these stories, it didn't move him," he said. "When he had an opportunity to address the court at the sentencing, rather than a simple word of 'I did it and here's why,' he stood silent."

McVeigh was convicted on federal murder charges and executed in Indiana in 2001.

Nichols was convicted on federal and state bombing-related charges and is serving multiple life sentences at a federal prison in Colorado.