Norfolk Constabulary's major investigation team has arrested three local males in their early 20s in connection with the murder of Barclays Wealth chief operating officer Frank McGarahan.
McGarahan died from injuries sustained after he intervened to stop an assault on a Lithuanian homeless man in Norwich city centre on Sunday.
A spokesman said the arrested men would be questioned on Tuesday night into Wednesday. But police have told reporters they do not want people to think this case is now closed and anyone with any further information should come forward.
Police say McGarahan, 45, was out with family and friends ahead of a family christening in Norwich. "He witnessed an assault whilst queuing for a taxi on Guildhall Hill, after which he sustained a fatal injury," says a police statement.
McGarahan died at Addenbrookes Hospital on Monday. He is survived by his wife and two daughters.
Mr McGarahan joined Barclays Capital in 1998, having previously worked at Deutsche Bank.