A police officer has been left seriously injured following an axe attack by a man who was "chopping bits off her", according to a member of the public who dragged her to safety.
The female officer, who has not been named, lost a finger when she was attacked with a hatchet in the Gleadless area of Sheffield, and also suffered a fractured skull and a broken leg.
She was the most seriously hurt of five police officers injured in the incident on Wednesday night after she and male colleague responded to what they thought was a "routine" domestic incident.
The incident began at a flat but finished in a nearby Co-op store where the attacker - described as a large man who looked like a bodybuilder - was finally subdued by officers using batons and a Taser.
Simon Ellis, 46, described how he witnessed the attack and then pulled the stricken officer into his flat as she feared the man would kill her.
Mr Ellis said he had first noticed two officers running up the stairwell in his block of flats in Plowright Close and then a woman resident emerged.
"She was saying that her boyfriend was in the process of chopping up some coppers and trying to kill them," he said.
"She said he'd lost his mind, the aliens were chasing him and he was trying to kill the police officers that I'd just seen running up the stairs."
Mr Ellis said: "As she did so, the lady police officer, who's been injured the most, came half-staggering, half-falling out of the stairwell pursued by this big bloke, this bodybuilder, with an axe.
"It was a frenzied attack, chopping at her with the axe. She was on the floor with her baton up, pleading for somebody to help her, to stop him hurting her."
He said the injured officer shouted: "He's going to kill me, get him off me."
"He was chopping bits off her," said Mr Ellis, who is a locksmith.
He said: "It was at least half a dozen to eight swings of the axe. He wasn't holding back at all. It was a full-blooded, frenzied attack with a hatchet.
"He actually was measuring his blows. He even waited for her to move her arms so he could get another chop in."
Mr Ellis said: "She thought he was going to kill her.
"She said 'He's going to finish me off, he's going to kill me, you're going to have to get me out of here. Drag me, drag me'. So I dragged her by her body armour with blood pouring out everywhere."
He said paramedics worked on the officer for more than an hour in his hallway, which is now covered in blood.
The attacker fled from outside the block of flats when the badly injured officer's colleague arrived and shouted at him, waving his baton.
Asked what the officer shouted, Mr Ellis said: "Like you would at a mad bull - which is exactly what he (the attacker) was. Just a complete psycho."
The man then made his way through an underpass to a Co-op store on the other side of the road where he began throwing objects at staff, customers and police.
Mr Ellis rejected suggestions that he was a hero who saved the woman's life.
"I'm not having that," he said.
"If I helped, that's all I'm bothered about. I'm not being dramatic. I just want to make sure she's all right."
Chief Superintendent David Hartley said armed officers were on their way to the scene at the time of the arrest but were not deployed.
Speaking at the scene, Mr Hartley said the woman officer suffered "grave injuries" but was conscious and facing surgery later on Thursday. He said she "remains in good spirits".
Mr Hartley said she was single, with no children, and had about 10 years' service.
The senior officer said all the other injured officers were well enough to be still working on the case on Thursday morning.
One of them - the officer who answered the initial call with his female colleague - was the first to be attacked by the man as the door opened in the flat and before he reached for the axe.
The other three officers were injured at the Co-op as they tried to restrain the man.
Mr Hartley said he had heard reports of the brave actions of members of the public to help his officers and he hoped to be able to thank them personally later in the day.
He said: "Whenever any of our colleagues face that ferocity and level of violence it does send shockwaves.
"We expect risk, and part of our job is to come between the public and harm. I have enormous respect for the team of officers last night who did just that - no hesitation at all putting themselves between the public and harm.
"And showing incredible bravery, bringing a man who was clearly intent on potentially killing someone into custody."
A man in his 30s remains in police custody after he was arrested on suspicion of the attempted murder of a police officer.
Mr Hartley said the incident was not related to the murder of a 22-year-old woman in Gleadless on Tuesday.