Frank McGarahan died in hospital the day after the attack
The brother of a banker fatally injured while trying to help two people being assaulted said he paid the "ultimate price" for being a good citizen.
Frank McGarahan, 45, chief operating officer of Barclays Wealth, died after suffering head injuries in the attack in Norwich, early on Sunday.
Norfolk Police have arrested three local men, aged in their early 20s, in connection with the death.
Tony McGarahan said his brother's death was a "mindless murder".
He said his family would "never truly recover" from the loss and added his brother "did what was natural to him to try and help someone because they needed help".
"He would not and could not stand by and watch a defenceless young lad and his girlfriend, who were in a taxi queue after enjoying being out together, being mindlessly attacked by a large group of grown men," Mr McGarahan said.
Strip club bouncer
"We will always be proud of Frank and we will never ever forget him.
"We will never understand how or why anyone could murder such a decent, caring and loving man."
Mr McGarahan said his family's immediate priority was to care for his brother's wife and children.
Tony McGarahan described his brother's death as 'mindless'
He urged anyone with information "however small and insignificant" to come forward.
Meanwhile, the arrested men are currently in custody in police stations across Norfolk and will be interviewed later.
Norfolk Police said Mr McGarahan, from Hertfordshire, had been spending an evening out with friends and family.
He witnessed a 35-year-old homeless Lithuanian man, who was walking his dog, being attacked while he walked with his girlfriend, 45, from Norfolk, police said.
Officers added that a bouncer from a nearby strip club, Darryl Lawton, had his jaw fractured after intervening in the fight, which involved Mr McGarahan, his brother and cousin.
Det Supt Chris Hobley said: "(Mr McGarahan) witnessed an assault while queuing for a taxi on Guildhall Hill, after which he sustained a fatal injury.
"Officers are reviewing CCTV footage from around the city centre area and following up a number of lines of inquiry."
Barclays Wealth employs 7,700 staff in 20 countries and manages assets worth £133bn.
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