A “peaceful and vulnerable” man was beaten to death with a blunt instrument, according to detectives.

Jon Ellison, 48, was found by friends on the floor near his bed in his flat in Gloucester Street, Brighton yesterday.

Police described the injuries as “some of the worst” they have ever seen and have spent the last two days looking for the weapon used.

Detectives have also published CCTV images of four people they believe may be vital witnesses.

Officers were called just to the ground floor flat about 2.10am.

They confirmed he was clothed and detectives are still establishing whether anything was stolen. There was no sign of forced entry.

Detective Chief Inspector Trevor Bowles, of Sussex Police Major Crime Branch, said: “Jon was by every account a peaceful and vulnerable man, and it is terrible that his life has been taken in this brutal way.”

The post mortem, carried out last night, confirmed that Jon died from several substantial head injuries believed to be caused by a long blunt instrument.

Defence wounds were apparent on his hands.

Police have been continuing to search nearby streets and premises for a murder weapon and any other possible evidence.

DCI Bowles said: “He was clearly subjected to a most vicious beating sometime between about 8pm on Thursday evening and just after 2am on Friday morning.

“These are amongst the worst deliberate injuries my colleagues and I have ever seen and they further demonstrate how important it is that we find the person or persons responsible as soon as possible.”

The CCTV images issued some passers-bys who detectives believe may be vital witnesses.

They were taken in St Georges Mew's, passing one of the entrances to the Gloucester Street flats, at 10.05pm on Thursday.

One appears to show a man, woman and teenage girl while the other shows a cyclist.

DCI Bowles said: “There is no suggestion whatsoever that they are suspects, and we ask them to come forward and talk to us in confidence.”

Anyone with information is asked to call 0845 60 70 999 quoting Operation Felsham or independent charity Crimestoppers on 0800 555 111.