Detectives investigating the murder of a "vulnerable" 33-year-old who was found with more than 100 separate injuries have renewed an appeal for help from the public.
James Attfield, of East Bay, Colchester died last Saturday after he was found with serious injuries in Castle Park just before 5.45am.
A 38-year-old man, from Colchester, was arrested on Wednesday and later released without charge.
Essex Police spoke to about 50 people at the murder scene last night and said they want to trace a man and a woman who would have been sitting on a bench in the park at about 11.30pm on Friday night.
Mr Attfield, who suffered a severe brain injury in a road accident four years ago, died in Castle Park, Colchester, last Saturday morning.
A post-mortem examination revealed 102 separate wounds on his arms, hands, back, neck and head.
Detector Chief Inspector Simon Werrett, who is leading the investigation, said today that extensive investigations are continuing in a bid to find the killer.
Police were at the murder scene from about 9pm last night until dawn this morning, talking to people who might have been in the park at the same time last Friday.
Mr Werrett said: "We spoke to about 50 people during the course of the night and we have been given some useful information that is currently being followed up.
"We also want to trace a man and a woman who would have been sitting on a bench in the park, by the lake. The only description is they were white and may have been smoking. This would have been about 23.30 on Friday evening.
"We also want to hear from anyone who may know someone who returned home early last Saturday morning with blood-covered clothing which they may have disposed of quickly."
Mr Werrett said that forensic investigations and searches were continuing in the park today and that officers were also searching a council tip for the contents of bins from the park that were emptied at the refuse site during last week.
Mr Attfield was a father of five, who had not been in contact with his children since he was severely injured when he was struck by a car.
His mother, Julie Finch, described her son as a "bit of a loner" who was "in the process of rebuilding his life" when he died.
CCTV showing Mr Attfield's last known movements was released by detectives on Monday as they appealed to the public for help in finding out who attacked him and why.
The film shows him at the River Lodge pub in Middleborough, Colchester. He left there at 10.09pm, leaving behind most of his drink, which his family say was unusual for him.
Police said they do not know where he went between leaving the pub and being found injured in Castle Park at 5.45am on Saturday.
At a press conference earlier this week Ms Finch spoke emotionally of how her son had battled to get his life back on track following the car accident.
She said the family ''gave him his independence'', adding that they ''didn't fuss over him, because that wasn't what he wanted and it wouldn't have helped him''.
Ms Finch said she last spoke to Mr Attfield ''face to face'' last year, "about October time''.
When asked whether Mr Attfield was in contact with his five children, Ms Finch said: ''After the accident he sort of had memory loss, and sort of wiped out basically six years before the accident.''
She said as they introduced information to him on the advice of doctors that ''he did get his children mixed up and think they were his brothers and sisters''.
Ms Finch added: ''Because the children were so young and he didn't really r emember them, he hasn't had any contact since the accident, no.''
She said her son was not a stranger to her in later years, adding: ''He knew we were always there.''
She said he wanted to be independent and lead his own life.
''He was always very quiet, and even as a child he was always a bit... cowardly, if you like.''
Mr Attfield was a karaoke fan and supported MK Dons football club.
Reading from a statement, Ms Finch said: ''Jim was well liked and polite - everyone always had a good word to say about him.
''I would ask the public for any information they may have that could help the police with their inquiries. This to me seems a senseless and frenzied attack on a gentle, vulnerable young man.
''Please, if anyone saw my son on Friday, please come forward. Someone, somewhere knows something. No matter how insignificant you may think it is, pleas e inform the police.''
Anyone with information is asked to contact the North Major Investigation Team on 01206 576845, 101 or Crimestoppers on 0800 555 111.