Donald Neilson, the Yorkshire serial killer who became known as the Black Panther, died from pneumonia.
Details of the 75-year-old’s final hours emerged yesterday as Norfolk coroner William Armstrong opened an inquest into his death.
Mr Armstrong told the hearing that Neilson was transferred from Norwich prison, where he was being held, to the Norfolk and Norwich University Hospital on Saturday.
Staff at the prison said the killer, who suffered from motor neurone disease, had been feeling unwell for two days and had reported shortness of breath, coughing and feeling cold.
He was pronounced dead at about 6.45pm on Sunday.
The inquest in Norwich heard that Neilson was vulnerable to pneumonia, partly as a result of his long-term condition.
The hearing was adjourned to a later date so more enquiries could be made. The independent Prisons and Probation Ombudsman will also carry out an investigation.
Neilson, who was born in Morley and lived in Bradford for 20 years, was given four life sentences in 1976 and was one of a small group of prisoners who were told they would never be released.
His early career was spent in the Army. He served in Kenya, Aden and Cyprus with the Kings Own Yorkshire Light Infantry before leaving in 1958.
He then embarked on a number of business ventures, including working as a self-employed joiner and setting up taxi and security firms.
But he found that he could make more money by using the covert skills he learned in the Army to commit burglaries and armed robberies.
Neilson’s first murder victim was Harrogate sub-postmaster Donald Skepper, who he shot dead during a robbery in February 1974.
He murdered two more sub-postmasters later that year, shooting Derek Astin in Accrington, Lancashire, on September 6 and Sidney Grayland in Langley, in the West Midlands, on November 11.
In January 1975, he abducted his fourth victim, 17-year-old heiress Lesley Whittle, from her home in Shropshire in January 1975.
The Black Panther left ransom notes, demanding £50,000 for Lesley’s safe return, but the girl was found dead seven weeks later.