The murder of Indian student Anuj Bidve at point blank range in Salford on Boxing Day is being treated as a hate crime, Greater Manchester Police have said.
Bidve, 23, described by his tutors at Lancaster University as an "outstanding" student, was gunned down as he walked with friends near their hotel in Salford, Greater Manchester, in the early hours of Monday.
Chief Superintendent Kevin Mulligan said on Thursday a racial motive had not been ruled out by detectives investigating the incident, but that no clear reason for the murder had emerged.
"We have not established a clear motive for the senseless murder of Anuj, and there is no definitive evidence pointing to it being racially-motivated," he told a press conference.
"However, we are treating this as a hate crime based on the growing perceptions within the community it was motivated by hate."
The murder weapon, believed to be a small handgun, has not yet been found, but Mulligan said there would be "no stone left unturned in trying to find those responsible".
He said police have secured a number of addresses in Salford and other parts of Greater Manchester that they have searched and are in the process of searching. Forensic and ballistics investigations are being carried out and police are trawling through CCTV.
The statement came after a fifth person, a 20-year-old man, had been arrested over the incident.
A 16-year-old boy, two boys aged 17 and a 19-year-old man are also being held on suspicion of murder.
Bidve was in a group of nine male and female Indian students visiting Manchester for a short break over the Christmas holidays.
Police said the students, who had not been drinking, were walking from their hotel towards the city centre and became aware of two men on the other side of the street.
The gunman, said to be a white male in his 20s who was wearing a grey top, walked across the road and engaged the victim in a short conversation before producing the gun and shooting the student at close range to the side of the head.
The killer then ran back across the street before the pair fled on foot towards Asgard Drive and the Ordsall housing estate.
Armed response units were sent to the scene at around 1.35am.
Bidve collapsed to the ground and died in hospital a short time later.
He was studying for a micro-electronics postgraduate qualification at Lancaster University, and was described by tutors as "an outstanding applicant at the very beginning of a promising career".
His family in Pune, Maharashtra, said they had "lost faith in everything" as they struggle to come to terms with the tragedy.
Members of Bidve's family have said they intend to fly to Manchester by the end of the week to take his body to India.
Tributes have been left on Facebook, including one page set up by a fellow Lancaster student which plans a "peace march" in Bidve's memory in the new year.
According to the page, set up by Sonakshi Saran, Bidve "was killed for not answering a simple question - 'What's the time?'".
Greater Manchester Police have not disclosed what was said during the short conversation between the killer and his victim.
Bidve arrived in the UK in September after completing an electronics degree at Pune University.
He was described as "clever and sporty", and a fan of football, supporting Manchester United.
The student's father Subhash, a branch manager with an energy company, has called on the UK government to speed up the process of returning his son's body to his home country.
Chief Superintendent Kevin Mulligan Mulligan said police were working with the Indian High Commission to help his family fly to the UK as soon as possible.
A spokesman for the Indian High Commission said that officers had visited Manchester for talks with the police and the body would be released for repatriation when the "investigation requirements" were completed.
On Wednesday Norman Owen, leader of Salford's Liberal Democrats, said the shooting had brought "shame" on Salford and called for police to "get into" gun crime.
Anyone with information is asked to call the incident room on 0161 856 5448 or Crimestoppers on 0800 555 111