Armed police are hunting for a man suspected of killing an off-duty policeman who was gunned down after intervening in a dispute near his home.
Pc Ian Dibell was shot dead and a member of the public sustained leg injuries after a gunman struck in a residential street in the seaside town of Clacton in Essex.
Police have released a photograph of suspect Peter Reeve, 64, and vowed to "not rest" until he is captured and taken into custody.
Peter Reeve, 64, who police are hunting for
Detectives from Essex Police launched a round-the-clock search involving armed response units and scores of officers after Pc Dibell, 41, was shot in Redbridge Road at around 3.40pm on Monday. The force said it had found the suspected gunman's vehicle at a nearby road junction and warned members of the public not to approach Reeve, who is believed to be armed.
Essex Police Chief Constable Jim Barker-McCardle described Pc Dibell as a "brave, respected and experienced neighbourhood officer" and said early indications were that he lost his life after deliberately intervening in an "extremely deadly situation".
He would not reveal the fine details of the altercation, but reports suggest the off-duty officer had challenged the gunman who was chasing a man and woman along Redbridge Road, where it is believed the dead policeman lived.
Speaking about Pc Dibell at the force's Chelmsford headquarters, the chief constable said: "This officer is a highly regarded and much loved colleague who has been a important part of Essex Police for 10 years.
"Policing is a family and we are all hurting. This dreadful event reminds us all that policing is a mission that ultimately some die for. We will not rest until we have Peter Reeve in custody, the investigation will continue round the clock."
The manhunt, being conducted alongside Kent Police, continued overnight, with local officers deployed to protect the public and maintain a strong presence in the area of the killing. A number of police helicopters were also involved in the operation.
A local resident said that she and her next door neighbour heard a woman screaming then what they thought were five or six gunshots. Another local, Eric Long, 80, said he saw the gunman from his window. He told reporters: "I saw him standing with some kind of revolver. He was chasing somebody, firing as he went."
Another local resident told the BBC that she and her next door neighbour heard a woman screaming then what they thought were gunshots.
"Then there was more shouting going on, screaming, from this woman, and then a man's voice shouting, quite really really loud shouting, then there was another series of gunshots, about five or six one after the other, then it went eerily quiet, just silence, and me and my next door neighbour just looked at each other, by then, and we thought, oh my gosh, was that actually gunshots we heard."
Reeve is described as white and about 5ft 10in with short greyish hair. He comes from the Clacton area and was wearing jeans and possibly glasses, police added.
Armed police at Farlop Close in Clacton where the incident took place on Monday
Eyewitness Andrew Gallehawk told ITV's Daybreak: "I saw a black guy running sort of towards my house.
"Next there was, it looked like a blonde guy, taking aim and made a couple of shots at him.
"Another guy flew past the house, sort of running, and that I assume now is the off-duty policeman.
"And then there were some more shots and then about five or six minutes after that there was a lady who seemed to be screaming in the middle of the road, and then we had all the police."
He added: "It was like one of those Clint Eastwood-type things where you've got the guy sort of crouching slightly on his knees and he's just taken a shot.
"I thought it was an airgun at first but obviously when I spoke to the police they said to stay in the house because it wasn't, it was live."
The gunman is still on the loose having shot dead one man and injured a woman
The former head of Essex Police's firearms unit, Mick Thwaites, paid tribute to Pc Dibell at the scene this morning.
He said: "It took huge courage and bravery. He responded to a call from the public with no consideration for his own life.
"He stepped in there to help someone in need and tragically, as a consequence of that, he lost his own life."
Mr Thwaites, who retired in 2009 after 35 years in the force, said the police would be using negotiators, dogs and officers armed with Tasers to trace Reeve.
He added: "The way (Mr Reeve) he has reacted to that situation by shooting two people - there are concerns as to his mental state and that will make it more difficult to find him."