Twelve people have been killed and another 25 wounded after a gunman drove across Cumbria shooting victims in several different locations, before taking his own life.
Police said they were investigating 30 separate crime scenes after taxi driver Derrick Bird, 52, attacked another man in Whitehaven and then embarked upon an apparently random shooting spree in the area.
The Queen tonight said she was "deeply shocked" by the shootings in Cumbria and shared the country's "grief and horror".
In a statement, police confirmed that Bird shot 12 people before killing himself. Another 25 people were wounded, three of those critically and five severely.
The first shooting was reported at 10.35am in the port of Whitehaven. Other incidents followed in Egremont and Seascale as police warned the public to stay indoors.
A manhunt took place for three hours as officers attempted to track down Bird as reports emerged of shootings in nearby locations.
Witnesses spoke of their terror as Bird drove through Whitehaven with the shotgun hanging out of the window of his taxi.
Police said that, after leaving the town, the gunman travelled south along the coast, shooting people in Gosforth, Seascale and Egremont before turning inland and ending up in Boot. Officers later recovered two weapons.
Deputy Chief Constable Stuart Hyde said it was a "truly exceptional" incident. The prime minister, David Cameron, promised the government would do everything it could to support the "shattered communities".
Police confirmed that a body found in a wooded area near the Lake District village of Boot was that of Bird. Two guns have been recovered. Hyde declined to comment on speculation that the first killing occurred last night, or that Bird had been motivated by an argument with other taxi drivers.
"The circumstances and the gravity of this demands that we have a full and comprehensive investigation," he told reporters in Whitehaven.
He went on: "Our condolences go out to families and friends of those affected by the horrific incidents that unfolded today. These are local people and local police who knew the people killed and injured today.
"It's been a truly exceptional and challenging incident that Cumbria police has had to deal with today."
He added: "This has shocked the people of Cumbria and the country to the core."
Hyde asked for witnesses to contact the police, and said that a helpline had been set up on 0800 096 0095 for concerned relatives of those involved in the incident. Cumbria police also set up a casualty bureau line on 0845 3300 247 and appealed for anyone with information about Bird's movements over the last 24 hours to contact them.
Earlier, police said those who were sheltering could now venture out, and thanked them for "their patience in incredibly difficult circumstances". They added: "Please be aware there are a number of crime scenes across the county and we would ask for people's patience whilst we conduct our investigations."
Cameron told the Commons: "The government will do everything it possibly can to help the local community and those affected and to keep the House informed.
"When lives and communities are suddenly shattered in this way, our thoughts should be with all those caught up in these tragic events, especially the families and friends of those killed or injured."
There would be a full statement in the Commons tomorrow, he said.
Jamie Reed, the Labour MP for Copeland, said the community was exceptionally close-knit. "This is a paralysing shock for us all, " he said.
Helen Owens, who works at the solicitors Brockbank, Cain and Hall, said one of her colleagues saw a dead man on the street: "We heard a couple of gunshots and the police running about.
"One of our secretaries was out at the time and she saw a guy lying dead on the ground covered with a sheet – she saw his trainers sticking out."
Bird was self-employed and lived alone, said Sue Matthews, a telephonist at A2B Taxis in Whitehaven.
She said: "To be honest, he was a quiet fellow. I am in absolute shock ... It is like watching something from America. I know him through work, he was self-employed but it's a small place.
"I know he had one son, who was grown up, and he lived alone. He was a regular in town and would have a night out.
"I would say he was fairly popular. I would see him once a week out and about. He was known as Birdy."
Rod Davies, landlord of Gosforth Hall Inn, said the close-knit Cumbrian communities were shaken by the tragedies.
"There's a lot of very strong feeling of absolute shock. There's a lot of fear - a lot of people are expecting to hear names of people they know," he said.
Bird was said to be close to a fellow taxi driver he killed in Duke Street, Whitehaven, as he started his rampage at about 10.30am.
Glenda Pears, owner of Whitehaven firm L&G Taxis, said Bird drove past one of her female drivers immediately after the first shooting, with a gun hanging out of his cab window.
She said: "One of our drivers saw him in the car and had to swerve to avoid him.
"He was driving, and she saw the gun. She was hysterical and had to pull over and stop. The gun was hanging out of the window."
She said staff were all "numb" after hearing of the tragedy, and added: "We're just in shock really. You don't expect something like this to happen in such a small town."
She described Bird as a man who enjoyed having a joke with others on the Duke Street rank, and said scuba diving was his hobby. He was also said travelling, and visited Thailand each year.
Many taxi drivers wanted to distance themselves from Bird today however, with one saying: "We don't want to be associated with scum like him."
One Whitehaven cab driver said he understood a total of three taxi drivers had been shot, two fatally.
The man, who did not want to be named, claimed an argument broke out between Bird and the other three men last night at the Duke Street taxi rank.
He said: "All of the taxi drivers were friends. But I heard last night there was an argument on the taxi rank.
"I don't know what caused it, but something must have happened last night. Derrick Bird took off in his car and went home. I don't know what time of night it was."
He said he knew one of the victims, describing him as "a real character".
The taxi driver, who had known Bird for 10 years, added: "He was quite a friendly person. This has been a shock to all the taxi drivers. It's just a tragic thing."
One witness said the gunman drove up alongside him at traffic lights by Whitehaven police station in Duke Street.
Alan Hannah, 68, of Great Broughton, told the Whitehaven News: "A car pulled up on the left, stopping at the lights.
"I saw a man with a large shotgun and his windscreen was smashed. I drove through the red light to get into Lowther Street and get out of the way. I got home safely but was very shaken."
A man reported finding the body of another of Bird's victims - a woman in her 60s carrying shopping bags - outside his house in Egremont.
Billy Boakes, 23, did not see the shooting but heard two gunshots at around 11am.
He said: "I thought nothing of it at first, I thought it was just a trailer banging as it went down the lane but then I looked out the front window two minutes later and saw a car and a push bike parked up and thought there had been an accident.
"I went outside and saw the body of the woman lying outside my house."
Another Egremont resident said she saw the body of a man, thought to be in his 60s, lying on a road bridge in the town.Bird crashed and dumped his car at the Boot Inn, continuing on foot into the woods where his body was found.
Early reports suggested that Bird also killed his mother, but Cumbria police later confirmed that she was alive and being looked after by her family.