Police have launched a manhunt after an officer was held down by two men and had his throat cut by a third.
Cleveland Police said they have identified a suspect they want to trace in connection with the incident.
The force have appealed for information about the whereabouts of Aaron Gray, 30, who is thought to be in Middlesbrough, following an attack on an officer who had tried to make an arrest.
The officer witnessed what he thought was a drug deal in Athol Street, Middlesbrough, at around 8.30pm on Saturday, and tried to intervene.
But he was punched to the ground and pinned down by two suspects. The man who hit him then held a knife to his throat and cut it while making threats.
Cleveland Police said the identities of two of those involved are currently unknown but they "urgently" need to locate Gray.
Detective Superintendent Helen Barker said: "This was an incident which involved an officer who was simply carrying out his policing duties.
"Thankfully he was not seriously physically injured; however, understandably, he remains very shaken.
"He is recovering at home and has received many messages of support from colleagues across the force.
"We need to locate and speak to Gray as quickly as possible.
"We believe he remains in the local area, probably within Middlesbrough.
"People will know where he is, and I’d urge them to pass information to Cleveland Police via the 101 number."
In an unrelated incident, a police officer in North Ayrshire, Scotland, suffered serious injuries after a car was driven at her in an attempted murder in the early hours of the morning.
The uniformed officer, a 28-year-old woman, and a uniformed colleague were in Eglinton Place, Kilwinning, when the incident happened at about 1.30am on Tuesday.
They were on their way to help colleagues with an inquiry when a blue Ford Focus was deliberately driven at one of them.
The 28-year-old officer was hit by the car and sustained serious leg injuries.
She was taken to University Hospital Crosshouse in Kilmarnock for treatment. Police are treating the incident as attempted murder and appealed for information as they hunt the driver, who fled the scene.
Detective Inspector Stephen McCulloch of Saltcoats CID said: "Our thoughts are with the constable, her family and colleagues and we continue to offer them all the necessary support.
"This incident is being treated as attempted murder and we will use all tools at our disposal to trace the person responsible.
"Anyone with information which might be relevant, who may have seen the car since or was driving in Kilwinning town centre in the early hours and has dashcam footage, is urged to get in touch.
"Information can be provided to Police Scotland via 101, quoting incident 0217 of 22 June, or anonymously to the independent charity Crimestoppers on 0800 555 111."