It appeared the taxi driver had only just missed seeing the attacker, Mr Miller said.
A post mortem examination would be carried out on Mr Cottrell this afternoon, and police said the brittle bone disorder he suffered from would not have contributed to his death. "They were severe injuries,'' he said.
Police moved to reassure the Wellington public that they should not be alarmed.
Mr Miller said this was the first homicide in a public place in Wellington this year, and there had been one other homicide last year in a public place: "This is an assault which cannot be predicted, it's unprovoked.''
He said there was no CCTV coverage of the assault, but there was footage of the area of Boulcott St, which police would work through today.
World traveller
Mr Cottrell had travelled the world only to be killed as he walked home in broad daylight in Wellington at the weekend.
He suffered massive head injuries and underwent surgery to relieve pressure on his brain.
However, the damage was too extensive and his life support was turned off yesterday.
Cottrell was a Briton but had lived in New Zealand for about five years.
A former colleague said he preferred to work overnight shifts so he could store up leave to take his "legendary'' travels.
"Phil was by far the most well-travelled journalist in the newsroom,'' she told APNZ.
"He had a pack-a-bag-and-go mentality. He was an adventurer at heart, I think.''
The manner of his death in what was regarded as a safe part of the capital, in daylight, was desperately unfair, she said.
"It's been hard to fathom that someone who had visited nearly every corner of the globe found such brutality just around the corner from work.
"It's incomprehensible.''
Cottrell's wallet was taken in the attack, and police were today viewing CCTV footage from the area.
Detective Senior Sergeant Scott Miller said there was no footage of the attack but there was of many parts of the street. Police were working through it, and a clearer picture of what happened was emerging.
"We've concluded our forensic scene examination and we're going through our exhibits from that scene with our experts,'' he told RNZ.
"We'll be carrying on with our area inquiries right through Boulcott St and in the central city area and continuing with an extensive search with our specialist search police through that same area.''
Radio New Zealand head of news Don Rood said "naked greed'' appeared to be behind the attack.
"I've heard that some items were stolen and it just makes it even more callous that someone's life is worth a few dollars and a credit card. It's just pathetic,'' he said.
"Phillip wasn't the sort of person that would go around provoking trouble, he was not that sort of person. He was not aggressive, he was not antagonistic, he was ... a nice guy that you wouldn't ever think of as someone who would be like that.''
The RNZ team was deeply affected by his death and the newsroom was unusually subdued yesterday.
"Journalists are used to trying to remain dispassionate and reporting on things from outside. When you're actually involved on the inside, when it's one of your own, it's just gut wrenching,'' Rood said.
"It was an appalling act of violence on one of our employees.''
Earlier yesterday, a large number of Mr Cottrell's colleagues gathered at Wellington Hospital to offer support.
His Te Anau-based sister and brother-in-law had rushed to Wellington, and were also being supported by Mr Cottrell's wide circle of friends, Rood said.
It was not known whether his parents would come from Britain.
Radio New Zealand chief executive and editor-in-chief Peter Cavanagh said staff were "devastated" this morning.
"Radio New Zealand is quite a large organisation but in some ways we are still quite a small family," he told Morning Report.
"We work and play together. We know each other very well."
Mr Cavanagh said Mr Cottrell's work as the overnight news editor was the "bread and butter" for the public broadcaster.
"He was a really fine journalist and a really fine writer."
Mr Cavanagh said there would be counselling services available to staff.
"It makes you sick to the pit of your stomach to think that there could be such a senseless unprovoked attack on someone in broad day-light, in what is quite a quiet part of Wellington."
Radio New Zealand host Lloyd Scott, one of the last people to see him, told TV3: "He would be no threat to anybody - somebody said to me yesterday, one of his friends, 'I think he's the nicest person I've ever met'."
Cottrell had a rare medical condition that made his bones fragile.
"Even if he'd been pushed and his head bashed against the wall and he fell down on his arm that might have caused the horrendous injuries he ended up with," said Scott.
Former RNZ presenter Sean Plunket said last night he was in shock over Cottrell's death.
"He was a thoroughly nice bloke, really nice. He really was a lovely guy.
"He was very unassuming, the last person you'd think this would happen to. If someone confronted him, he's not the type of guy who would provoke them."
Cottrell worked at the BBC in London and Scotland before moving to New Zealand.
His friends and former colleagues at BBC Scotland said he was "a gentle, kind man with an impish sense of humour''.
"He was a brave traveller, forever venturing to new countries and exploring new cultures,'' they said in a statement published on BBC News.
"He leaves behind many, many friends in every corner of the world who will be distraught to learn of his loss.''
Cottrell's friends in Scotland were "devastated'' at his senseless death and said their thoughts were with his family, friends and colleagues in New Zealand.
