An argument with a group of youths which got out of control may have led to a pensioner's murder, police say.
Police investigating the death of Alan Irwing, 74, in High Wycombe, Bucks, believe the argument may have erupted over a misunderstanding.
Mr Irwing, a widower, of Underwood Road, was found by neighbours lying near his front door in a pool of blood.
He died in hospital after suffering injuries in an attack which took place on Thursday.
Two men aged 17 and 18 were arrested on Thursday but later released on bail pending further inquiries.
Three others - a boy aged 14 and two men aged 18 and 19 - held over the weekend were released without charge.
No weapon used
Shouts were heard and neighbours ran to the widower's aid to find him lying on the pavement around 50 yards from the front door of the house he had lived in for decades, police said.
Unable to get a response as they called out to him, neighbours alerted emergency services and he was taken to Wycombe General Hospital, where he later died.
A post-mortem examination found that Mr Irwing died of multiple injuries which had not been inflicted by a weapon.
Messages left with flowers at the scene of the attack described Mr Irwing's death as senseless, with one card asking simply: "Why???"
No weapon was used in the attack and detectives are not treating the killing as a mugging which went wrong.
A spokeswoman for Thames Valley Police said officers were looking at the possibility that Mr Irwing may have been drawn into an argument with a group of youths.
It is not yet clear whether he was attacked by a single member of the group or more than one.
She said officers were examining the possibility that there had been a "misunderstanding" on the part of the youths which led to the argument and ultimately ended in tragedy.