BOSTON (CBS) – Agents say Rezwan Ferdaus started planning his jihad on the United States early last year.

His first step was buying cell phones and modifying them to act as electrical switches for improvised explosive devices.

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In December 2010, he first contacted someone, who was a federal informant.

WBZ-TV’s Kate Merrill reports

Then, in January of this year, they recorded Ferdaus, speaking to that informant, about plans to attack the Pentagon.

In March, undercover FBI agents, posing as members of al Qaeda, met with Ferdaus for the first time.

Read: Who is Rezwan Ferdaus?

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In April, agents say Ferdaus expanded his attack plans to include the U.S. Capitol, and in May, he flew to Washington to do some surveillance of targets.

Around the same time, he gave the undercover agents thumb drives, with step by step plans.

Ferdaus ordered a remote controlled aircraft, and last month it arrived at the Framingham storage facility he had rented with cash.

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On Wednesday undercover agents gave Ferdaus what he thought was 25 pounds of the explosive C-4, as well as AK-47’s and grenades.

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Right after he accepted the weapons, the agents arrested him.

Kate Merrill