Federal authorities are searching for a suspected bank robber who they have dubbed the “bare-chested bandit” since he was apparently seen changing clothes following at least one robbery.The suspect, a man in his 30s, is accused of handing a note demanding funds to a bank teller at the Citibank at 100 S. Michigan Ave. around 4 p.m. Tuesday. He made a violent threat before obtaining money from the bank and fleeing, the FBI said.He’s also accused of robbing the Citibank at 180 N. Michigan Ave. about 9:45 a.m. Sept. 16 and again around 2:30 p.m. Sept. 19.“Though this suspect has worn a different ‘disguise’ for each incident, this is the first incident in recent years where we have observed a suspect changing clothes on public transportation,” the FBI said in a statement. Federal authorities are searching for a suspected bank robber who they have dubbed the “bare-chested bandit.”FBI The suspect is described by the FBI as a white man between 30 and 40 years old, about 5-foot-6, medium build with an armband tattoo on his upper right arm.He wore a dark plaid jacket, a white collared shirt, light colored jeans, a black hat, mirrored sunglasses with a black frame, and black and white athletic shoes during Tuesday’s robbery, according to the FBI.Anyone with information about the robberies or the suspect’s whereabouts is asked to submit a tip to the FBI at 312-421-6700 and tips.fbi.gov.