Detectives have launched a murder investigation after a young man beaten up following an argument in a McDonalds restaurant died in hospital.The 21-year-old victim suffered head injuries in the attack at the branch in Haymarket, Norwich, at about 8pm on Wednesday.

Detectives have launched a murder investigation after a young man beaten up following an argument in a McDonalds restaurant died in hospital.

The 21-year-old victim suffered head injuries in the attack at the branch in Haymarket, Norwich, at about 8pm on Wednesday. He was pronounced dead at about 6pm on Thursday at the Norfolk and Norwich University Hospital.

Two men believed to be father and son are being questioned by police. An 18-year-old, from Norwich, was arrested just after 8.30pm in the Aylsham Road area of the city on suspicion of assault causing grievous bodily harm. He is being questioned following the incident at about 4pm at McDonalds restaurant in the Haymarket

A 48-year-old man was arrested also on suspicion of assault causing grievous bodily harm at the scene of the incident and is being quested at a different police station in Norfolk.

The older of the two men was apprehended by heroic staff who gave chase after watching the drama unfold. Three workers caught the man and waited for police to arrive. On of them, Shaun Ross, 17, said: “We ran across when we saw what was happening and chased them out.

“The son got away but we caught his dad and kept hold of him until the police came.”

Witnesses should contact officers at Norwich CID on 0845 456 4567.