WHEATON, Ill. (CBS) — The Wheaton bandit is now officially off the hook, but the FBI says that doesn’t mean the case is closed.

As WBBM Newsradio’s Regine Schlesinger reports, at midnight, the statute of limitations expired on the 16 robberies blamed on the single serial robber, who preyed on suburban banks and credit unions between January 2002 and December 2006.

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LISTEN: WBBM Newsradio’s Regine Schlesinger reports

His modus operandi was to walk into a bank wearing a mask and point a gun right away at employees or customers as he demanded money from tellers. He parked his car about a block away so no one at the bank could see him leave.

He hit banks in Wheaton, Carols Stream, Winfield, Glen Ellyn, Naperville and Geneva.

FBI spokesman Ross Rice says the bureau may never know why the string of holdups suddenly stopped, although there are plenty of theories.

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He believes the robber most likely became afraid police were closing in.

“Others think that he may have been in the military and got called to active duty and is overseas. Others think he might have been incarcerated on an unrelated charge,” Rice said. “We just don’t know.”

In any event, unless the Wheaton Bandit starts robbing banks again, he is now beyond the reach of the law.

Still, Rice says investigators will pursue any new leads that might come in.

“We would like to put an end to the case,” he said. “We would like to be able to say we know who did it.”

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The FBI had been offering a $50,000 reward in hopes that a suspect could be caught before the statute of limitations ran out.