Investigators say Nafis selected his target, drove a van loaded with 1,000 pounds of dummy explosives up to the door of the bank, and tried to set off what he thought was a bomb.
They say he used a cellphone he thought had been rigged as a detonator.
But it was all fake. It was part of a federal undercover sting operation.
He told the judge in a letter he was extremely sorry for what he had done.