By Ben Brumfield, Pamela Brown and Dana Ford, CNN

(CNN)For months, 20-year-old Christopher Lee Cornell had been on the FBI's radar. Authorities said he left alarming posts on social media, talking about violent jihad.

Authorities say Cornell, who ostensibly tweeted under the name Raheel Mahrus Ubaydah, hatched a simple scheme. It was similar to the Paris attack on the offices of Charlie Hebdo, but at a key location -- the U.S. Capitol, said a criminal complaint filed by an FBI agent.

The plan: Set off pipe bombs to put lawmakers and employees in panicked flight and then gun them down with an assault rifle as they ran across his path and that of an accomplice, Special Agent T.A. Staderman wrote.

Cornell was ready to go, the agent said.

He had made preparations with a partner. He had researched bomb-making instructions and by Wednesday, Cornell had bought two M-15 rifles with 600 rounds of ammunition.

But the man Cornell believed was his partner was actually an FBI informant, a man in trouble with the law who worked with the agency to improve his legal standing.

 

Read More: http://www.cnn.com/2015/01/15/us/capitol-attack-plot/index.html