Police have said they do not know why a church organist was killed on Christmas Eve and have released CCTV in a fresh appeal for information.
Grandfather Alan Greaves was attacked on his way to midnight mass in High Green, Sheffield, only a few hundred yards away from his house.
He died from severe head injuries three days later.
Detective Superintendent Matt Fenwick was speaking as he released CCTV footage of two men his officers want to speak to.
Speaking at a press conference in Rotherham, the detective said: "I still have not established a motive for the attack. Alan retains all his property. Nothing is missing and my inquiry remains very open in relation to identifying a possible motive for this attack."
Mr Fenwick said there was nothing in the victim's personal life which would point to a motive.
He said more than 50 officers are working on the case.
Mr Fenwick said the two people in the footage "may be able to assist us with our inquiries."
Two men have been arrested in connection with Mr Greaves's murder and bailed pending further inquiries.
Mr Fenwick said the people featured in the CCTV footage are not anyone who has been arrested so far by the investigation team.
He said he could not be too specific about exactly where the footage was taken but he said it was within hundreds of yards of the scene of the attack.
The detective said it was "just before" the incident.
Mr Fenwick said no weapon has been recovered. He said he was confident a weapon was used to attack Mr Greaves but could not say what it was.
He said: "If you are either of these two people shown on the footage then please contact the incident room as soon as you can.
"If you know, or can identify either of these two people, please pick up the phone and tell us what you know.
The detective said: "Alan was a loving, caring, husband, father and grandfather who was well-loved and respected by all who knew him."
He rejected any suggestion the investigation might have got off to a slow start because it happened at Christmas.
He said there had been no problems assembling an investigation team as would be normal in any murder investigation and added: "People can't give enough time to try and assist this investigation. We had no problem or difficulty at all."
Last week independent charity Crimestoppers put up a £10,000 reward to help find those responsible for Mr Greaves's death.
The reward will be available to anyone providing information to Crimestoppers leading to the arrest and conviction of any person or persons responsible for Mr Greaves's death.
At a service after her husband's death, Mr Greaves's widow Maureen said she had wept over the "evil that has been done".
She told the congregation of St Saviour's she had felt their love and support since her husband died.