A US citizen has been arrested in Italy on suspicion of murdering a shop owner in a town near Rome.

The body of Norveo Fedeli, 74, was found in his clothes shop in Viterbo on Friday. Italian media reported he had been struck repeatedly over the head with a stool.

Police had released video surveillance of a young man wearing sunglasses and a back-to-front cap who was carrying a shopping bag close to the scene. On Saturday they arrested Michael Aaron Pang, 22, at a bed and breakfast in the nearby town of Capodimonte. He allegedly had small cuts on his hands and face and traces of blood on his shoe.

Investigators said they had “strong evidence” to charge Pang, born in South Korea, with murder and robbery. “The investigations developed very quickly,” said the Viterbo prosecutor, Paolo Auriemma. “A detention order has been issued. A result achieved thanks to the coordination of several police units.”

Pang is reported to have been living in Capodimonte, a town by Lake Bolsena, since arriving in Italy two and a half months ago on a tourist visa. It is alleged he killed Fedeli because he was unable to pay for purchases from his shop, Fedeli Vogue, which had been open since the 1970s and was well-known for its vintage and designer jeans, according to Italian media reports on Sunday.

The Il Messaggero newspaper reported that Pang had visited the shop previously and on the last occasion had returned to collect designer clothes worth €600 (£510). Pang reportedly told residents in Capodimonte he was a graphic designer.

Giovanni Arena, the mayor of Viterbo, has declared Monday a day of mourning for Fedeli, who has been described as “a good and kind man”. “The murder of our citizen, Norveo Fedeli, has shattered us all,” said Arena.

The death came a few days after two members of the neo-fascist group CasaPound were arrested for allegedly raping a 36-year-old woman in a private club in Viterbo.