"I grew up on a farm using fertilizer, using ammonium nitrate many times. We would have from 20-60 tons in our barn," says Donald Isenhower. Isenhower is a professor of engineering and physics.
"There are warnings on it that you don't drop the sack. And you definitely don't get it too warm or it can explode," says Isenhower.
Even if you didn't grow up on a farm, he says the basic science is taught in high school chemistry.
"The explosives can be as simple as finding somethings like household chemicals you can mix to get an explosion," says Isenhower.
But of course, mistakes are highly likely.
"If the person is really ignorant, they're more likely to kill themselves than successfully make the bomb," explains Isenhower.
The recent events have made many worry about the need for heightened security.
"Well they could've run and checked everybody as they come up and down the sidewalk. And then everyone would be upset. It would make a very very messy situation," says Isenhower.
With possibilities lurking at every corner.
"There are large pipelines carrying natural gas, there are all sorts of things nearby and people live near them," says Isenhower.
We are reminded that some questions are better left as questions.
"People always want to come up with solutions, 'oh this will solve that one,' Well it might have solved that one, in that particular case at that particular time. But it won't solve something else that happens differently," says Isenhower.
Isenhower tells us too many factors have to go exactly right to create an explosive that would hurt a large number of people. He says most people are not capable of producing such weapons.