Bank robbed in Whittier, authorities suspect serial bandit

It appears the FBI is yet to name this newcomer to the field of serial bank robbery. Based on his height and M.O., I've already heard "Little Bomber Bandit" suggested. Any ideas?

WHITTIER -- A man threatened to have a bomb while robbing a U.S. Bank branch in Whittier Saturday in what police suspect was the second area bank robbery carried out by the same bandit in three days.
The crime took place about 11 a.m. at the bank at 13525 E. Whittier Blvd., Whittier police Lt. Bill Webster said.
A robber walked into the bank and approached a teller, Webster said, "threatening to have bomb and demanding money."
The demand was made verbally, as opposed to in a note, officials said.
After receiving an undisclosed amount of cash, the robber was last seen leaving the area on foot, police said.
He was described as a white man in his 50s, between 5 feet 1 inch and 5 feet 4 inches tall, with a thin build and wearing dark clothing and a dark beanie.
The tactics used in the robbery and the description of the suspect were strikingly similar to those reported in a Wednesday robbery at another U.S. Bank branch in Norwalk, Webster said.
"It's very similar to the one in Norwalk recently, so we believe it may be the same suspect," he said.
In Wednesday's crime, a man of a similar description entered the bank branch at 13928 Pioneer Boulevard in Norwalk, Sgt. Glenn Emery said.
He handed a teller a note in which he claimed to have a bomb and demanded money, official said.
In both crimes, the robber carried a brown, zippered portfolio.

PHOTOS: Above - surveillance image from Saturday's robbery in Whittier.(Courtesy of the Whittier Police Department) Below - a surveillance image from Wednesday robbery in Norwalk.(Courtesy of the FBI).