DENVER (CBS4) – On Tuesday, a day that a bank robber’s heist in Jefferson County forced the lockdown of three nearby schools, the FBI released its list of top 10 bank thieves along Colorado’s Front Range.

Topping this list is the so-called “Good Grammar Bandit” who may be behind at least seven robberies in Denver.

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Apprehending him is now of paramount importance, the FBI said. His calling card is a well-crafted note demanding money — or else he’ll become violent.

“He’s committed seven robberies, and we’re very concerned about that eighth,” said Mike Rankin, a special agent in charge in Denver.

The 10 men on the FBI’s list have robbed banks from Greeley to Colorado Springs. Some disguise themselves with glasses and hoodies. One armed suspect wore a full winter coat inside the bank. Others have been more brazen; one suspect took his glasses off and stared a teller directly in the eyes when he twice robbed a bank off Speer.

One of the most frequent targets is down the street from the FBI’s regional office in Denver. The FBI says Denver suffers the fifth-most robberies in the country.

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“We’ve had several individuals who have exhibited violence during bank robberies, have committed serial robberies, or people who could escalate violently,” Rankin said.

The FBI says no one has been hurt in robberies this year. They’re usually crimes committed with threats on notes instead of the barrel of a gun, but investigators say even the most benign incidents can become much more violent crimes.

“That individual may be carrying a gun, may have an explosive device, so we’ve got to get these guys off the street as soon as possible,” Rankin said.

Tuesday’s robbery occurred at a First Bank on south Wadsworth Boulevard in Littleton. The FBI described the suspect as a white man, 20 to 30 years old, about 6 feet tall and 130 pounds.

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Anyone with information about that heist is asked to call the FBI Rocky Mountain Safe Streets Task Force at 303-629-7171.