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Armed and extremely dangerous. Some heavy weapons have fallen into the wrong hands in Chicago– and police desperately want to get them back.

Perhaps ironically, these semi-automatic rifles are very similar to what police themselves use. Thirteen of them were stolen from a train parked in Englewood– complete with their high-capacity 30-round magazines.

Special Agent Tom Ahern, ATF: “They’re high-capacity rifles. They’re very dangerous when they’re in the wrong hands.”

The Smith and Wesson M and P 15 Sport Rifle– virtually identical to the M-4 assault rifle U.S. troops use at war, police use to keep the peace; or citizens use to create chaos, in the AR-15 Bushmaster Incarnation. That’s the now-infamous weapon used in the massacre at sandy hook elementary school.

Sometime between Sunday and Tuesday, 13 of them were grabbed from a shipment of 50, from a Norfolk Southern freight container parked at this Englewood rail yard.

Community Activist Andrew Holmes: “I’m demanding that a thorough investigation be done and the security firm that’s here be removed until this case is resolved just in case this was an inside job.”

Investigators seem to feel otherwise, that the crooks had no idea what they were taking. It’s not a security firm that works here, but Norfolk Southern’s own police force, now working with Chicago police and the bureau of alcohol, tobacco and firearms to get the guns back

They fire what’s known as a ‘NATO bullet’ essentially military caliber– 5.56 millimeter and while they don’t ship with those bullets; they do ship with magazines that carry 30 of them at a time, firing them off as fast as you can pull the trigger.

Tom Ahern “And we’re just hoping that these guns don’t get in the hands of more violent offenders that are gonna use them in crimes.”

They were just passing through on a train from Smith and Wesson’s factory in Springfield, Massachusetts to a licensed dealer in Minnesota.

What has law enforcement and politicians here so concerned is that these are exactly the kind of weapons and magazines they’re trying to keep off the streets of Chicago.