Twelve people have been killed by a gunman who went on the rampage across Cumbria in north-west England.
Taxi driver Derrick Bird shot dead a colleague in the town of Whitehaven before driving through the countryside apparently targeting people at random.
Twenty-five others have been injured, three critically. Police say they are dealing with 30 separate crime scenes.
Mr Bird's body was found in a wooded area in Boot in the Lake District and two weapons have been recovered.
Stuart Hyde, Cumbria Police's Deputy Chief Constable, said: "We are still at a very early stage in our investigation and we are not able to really understand the motivation behind it - or establish whether this was a premeditated or random attack.
"Current indications are that 12 people have died, plus Derrick Bird. And a number of people are also receiving treatment in hospital.
"We are working hard to support the families of those involved and our focus is now on gathering as much evidence as possible to build up a clear picture of what happened this morning."
Anyone concerned about the whereabouts of relatives should contact Cumbria Police's Casualty Bureau hotline.
After the first shooting, witnesses said Mr Bird drove through Whitehaven with a gun hanging out of his car window, then headed south through Gosforth and Seascale before turning inland.
As well as Whitehaven, fatalities have been confirmed in Egremont, Seascale and Gosforth.
The mass shooting is England's worst since 1987, when gun fanatic Michael Ryan killed 16 people in Hungerford, Berkshire.
As he began his first Prime Minister's Questions today, David Cameron said the House of Commons would be "alarmed and shocked by the events unfolding in Cumbria".
He said: "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."
After the killings, detectives said 52-year-old Mr Bird drove to the central Lakes in a Citroen Picasso, then abandoned it in the Boot area.
Before his body was discovered, people living nearby were urged to stay indoors for their own protection.
Helicopters and armed officers from other police forces were brought in to help apprehend the gunman.
Mr Hyde added: "We have a number of crime scenes across the county, which are being staffed by police officers, and I would ask people to show a little bit of restraint and respect in regard to those scenes as we try and piece together exactly what has gone on."
A major incident has been declared at West Cumberland Hospital, in Whitehaven, where the NHS said all routine operations had been cancelled.
The Accident and Emergency department at the Cumberland Infirmary in Carlisle is also on full incident stand-by, the hospital trust said.
The Sellafield nuclear reprocessing plant in west Cumbria closed its gates as a safety precaution and afternoon shift workers were being told to stay away, though the site has since reopened.
The Whitehaven victim, believed to be a colleague of Mr Bird, was killed at 1035 BST.
A local taxi firm boss, Glenda Pears, said: "We just don't know what's happened.
"The lad that's been killed was friends with him. They used to stand together having a craic on the rank.
"He was friends with everybody and used to stand and joke on Duke Street."
Sue Matthews, a telephonist at A2B Taxis in Whitehaven, said the Mr Bird was self-employed and lived alone. She described him as a "quiet fellow".