The four robberies and amounts taken included:
Hagerstown Trust Co., Boonsboro, Feb. 7, $2,138.
NationsBank in Leesburg, Va., Feb. 11, $14,747.
Virginia First Savings Bank in Richmond, Va., Feb. 19, $5,836.
F&M Bank in Winchester, Va., Feb. 20, $7,368.
The total taken in all four robberies was more than $30,000.
In a lucky break, Frederick City Police went to the Comfort Inn Motel on Prospect Boulevard in Frederick at 11:30 p.m. on Feb. 22 in response to reports of drug use in a room.
The officers encountered Knill, a registered guest at the motel. They found a quantity of money that was found to be the proceeds of bank robberies in Virginia, police said.
The FBI was brought in and through a cooperative investigation, Knill was implicated in the robbery of the banks in Winchester, Leesburg and Richmond, Va., as well as in Boonsboro, police said.
In the Feb. 7 Boonsboro robbery, the robber entered the Hagerstown Trust branch at 207 N. Main St. at 12:25 p.m. Maryland State Police described him as being slim and dressed all in black.
The robber, carrying a red six-pack cooler, waved a handgun, ordered everyone away from the alarm and demanded money from three tellers, police said. He stuffed the cash into the cooler, police said.
Knill, who repeatedly said he didn't want to hurt anybody, left the bank on foot, walked north on Ford Avenue and got into a gray or silver late 1980s model Toyota car, police said.
In each of the other robberies, Knill displayed a handgun and warned tellers not to sound alarms or to give him a dye pack, police said.