Police have called on the man who lay in wait before mugging two pensioners, one of whom later died, to give himself up.
James Connor (67), who lived at a flat in south Belfast, was attacked, beaten and robbed of his wallet in an alleyway near a Belfast city centre pub on Wednesday afternoon. He died later in hospital.
Shortly after that attack an 85-year-old pensioner was also assaulted and had his wallet stolen, probably by the same man, police believe.
They are trying to ascertain if a murder has been committed. Cause of death has yet to be established and a postmortem is being carried out.
Det Insp Jeff Smyth has urged the suspect to "examine his conscience" and "do the right thing and give himself up".
Police are looking for a dark-haired man aged between 30 and 40 years, about 178cm (5ft 11) in height and heavily built. He is also said to have been wearing faded denim jeans and a light-coloured jacket.
The PSNI has said CCTV film shows the attacker being pursued by a passerby before he threw the stolen wallet away.
Det Insp Smyth said: "I want to appeal directly to the suspect. Examine your conscience. What you did was horrendous. There is one elderly gentleman lying in a mortuary today and another gentleman at home trying to recover from his injuries, both of which were sustained at your hands." Both attacks were planned, he added.
He said Mr Connor had left the Mermaid Bar and was walking towards Ann Street when he was attacked from behind, struck on the head and fell to the ground. "We have at least one witness who has seen this male suspect rifle through the pockets of this gentleman's clothes and take his wallet.
"The suspect then ran off leaving Mr Connor lying injured on the ground."