Kevin Miles was with the FBI for 23 years and was stationed in Los Angeles for 17 years before retiring two months ago. He spoke on the inner-workings of bombing investigations and lessons to be learned from past bombings.
"No one is going to look twice at a person carrying two backpacks at a marathon, so that in and of itself tells me that this individual has got some experience and some intelligence on how to carry out an operation like this," Miles said.
Miles has experience as a team leader in some high-profile cases.
"The Oklahoma City, the World Trade Center bombings, the Khobar Tower bombings, the embassy bombings that I have been on in my career were gigantic, I mean they were truck bombs, there were thousands of pounds of explosives in each one of them," he said.
Boston's crime scene is actually much smaller, and the placement of the bombs is important.
"The devices were placed in front of buildings, so most of the evidence is going to be thrown out in a 180-degree arch, some of the evidence has probably gone into the buildings it was near, but the majority of the evidence is going to be out there in fairly decent distances," he said.
Finding the evidence is one thing, but identifying and finding the suspect is another.
"You might have in a situation in Atlanta, where it took several months, or the Unabomber, which took several years," Miles said.
The public fears these types of bombings are becoming the new normal for life in America, but Miles shed light on that perspective.
"Our new normal has been this way since Sept. 11," he said. "Granted, we probably got a little complacent over the years, but I think -- I've always thought -- that bombs are the No. 1 weapon for terrorists worldwide, and it's probably going to continue that way for a long time to come."