A war veteran was beaten to death by a dementia patient as he lay in a hospital bed, his family have said.
Richard Bowman, 86, was found in a pool of blood with severe head, leg and arm injuries after the incident at West Suffolk Hospital, Bury St Edmunds.
He died on Saturday, 12 days after the attack.
It is believed he had been attacked by the dementia patient who was wielding a bottle.
A spokesman for West Suffolk Hospital said: "We would like to take this opportunity to extend our sincere condolences to the patient's family.
"We are taking this incident extremely seriously and are carrying out a full internal investigation."
A Suffolk Police spokesman confirmed the force was investigating reports of an assault at the hospital on November 25.
A post-mortem examination found Mr Bowman's death was the result of natural causes and the death is not being treated as suspicious.
He said: "This matter will now be dealt with by the coroner."
Mr Bowman's family told the Daily Mail that Mr Bowman should never have been left alone with the patient.
His son Charles Hawes, 43, told the newspaper: "He was lying on his bed getting ready to fall asleep and this chap just came over and started laying into him with a bottle.
"He was much too weak and elderly to fight back."
Mr Bowman, from Exning near Ely, Cambridgeshire, served with the Royal Regiment of Fusiliers before running a number of businesses, including an estate agency.
He had been admitted to hospital with a chest infection.