Edward Klein, 79, was charged with discharge of a firearm causing great bodily harm and attempted murder.
Prosecutors said Klein had just returned from a canceled trip to Las Vegas, and was trying to catch a train to Milwaukee, but tried to get off the Amtrak train at a scheduled stop in Naperville.
Klein stayed on the train, but decided he wanted to get off after the doors closed.
Prosecutors say Klein told police he became angry when he couldn't disembark in Naperville, outside Chicago, and shot the conductor.
The release states that Edward Klein attempted to exit the train through the window, but he was detained by train personnel and Amtrak passengers.
Other passengers restrained the gunman until police arrived. The conductor remains in intensive care.
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He was taken into custody and a handgun was recovered, police said.
Klein will be back in court in Wheaton on June 12th.
State's attorney's office spokesman Paul Darrah said Klein formerly worked for the Federal Protective Services, a branch of Homeland Security that provides security for federal facilities.
They also said he admitted that he pulled a gun on people twice before during earlier confrontations.
Klein's status as a former federal law enforcement agent would not have exempted him from that policy, the spokesman said. "I would like to thank authorities with Amtrak as well as the Naperville Police Department for their quick response to this situation".
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