The factory is surrounded by wasteland and other industrial units
A police officer has died after suffering a gunshot wound to the chest on a training exercise in Manchester.
Pc Ian James Terry, 32, from Burnley, Lancashire, died in North Manchester General Hospital after the incident in Thorp Road, Newton Heath, at 1135 BST.
It was not immediately clear whether the officer had been shot accidentally by one of his own colleagues.
The Independent Police Complaints Commission (IPCC) has begun an investigation into the fatal shooting.
Pc Terry joined the force in 1997 and had been a firearms officer for six years.
Acting Chief Constable of Greater Manchester Police (GMP) Dave Whatton said: "Everybody in Greater Manchester Police is devastated by the news that we have all received and the loss of a highly regarded colleague and friend."
This demonstrates the dangers that police officers face on our behalf
Mr Whatton said a full investigation had begun and teams were working to preserve evidence at the scene.
He added there had been no risk to the public at any stage during the training exercise.
A GMP spokesman said the training exercise had been "reasonably routine" and that similar exercises happened "fairly frequently".
The IPCC has sent three investigators to the scene to carry out an initial assessment.
The area where the incident happened is the site of a disused former electronics factory, known locally as the Sharp Building.
Acting Chief Constable Dave Whatton says police are 'devastated' by the death
It was the former distribution centre for Sharp, the electronics giant, which used to sponsor Manchester United.
Police sealed off entrances to the site, but forensic officers in white overalls could be seen in the goods yard outside the warehouse, which was cordoned off with yellow tape.
An ambulance was also on site.
The factory is surrounded by other industrial units and wasteland and one of the main links into Manchester runs alongside.
Speaking in the Commons, Home Secretary Jacqui Smith told MPs: "The whole House will be saddened to learn of the tragic death today of a police officer during a training exercise with Greater Manchester Police.
"This demonstrates the dangers that police officers face on our behalf."
Brothers Haroon and Bilal Razaq, who work at a plumbing supplies shop near the site entrance, said they were alerted by police cars and an ambulance entering the site.
Haroon, 17, said: "All of a sudden there were police cars and an ambulance pulling skids and going round the corner on to the site.
The shooting was said to have happened in a "routine" training event
"There were six or seven police cars and they just shot past all the standing traffic. They were going really fast, so we knew it was something serious."
Bilal, 25, added: "We have been here for around three months and we thought the building was closed and Sharp had moved somewhere else.
"We have never seen an officer in uniform around here and we didn't know the police used it for training."
Leon Willis, 26, who was working in the same plumbing shop, said: "We have had the door open all day because of the weather and we heard a loud bang. I don't know if it was a gun shot or not."
Five UK police officers have been shot and killed accidentally with police firearms.
The last officer to die was Pc Samuel Lock, from the Metropolitan Police, in 1950, who was shot while cleaning a police pistol at a police station.
The last officer shot and killed by accident during a training exercise was Special Constable Arthur Guest in 1941, who was shot by an instructor.
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