Image shows US Police on duty.
He was pronounced dead at the scene in Southleigh Community Hospital, South London. The male nurse is yet to be formally identified by police as at the time of this report.
Southleigh Community Hospital is a private medical facility located on Brighton Road, south Croydon. The facility provides treatment and rehabilitation for adults with long-term mental health problems.
Further information says a 40-year-old man who police believe was a patient at the facility was arrested at the scene on suspicion of murder. He was arrested at around 2.40pm on Thursday.
The accused is currently being treated at another hospital in south London for an injury to his hand.
A Metropolitan Police spokesman said: “We believe the man arrested was a patient residing at the facility. We retain an open mind relating to the circumstances surrounding the incident.”
Another spokesman for the hospital said: “We are greatly saddened to confirm that a member of staff lost his life yesterday following an incident in the hospital.
“Our deepest sympathies are with his family, friends and colleagues. He was a valued and respected member of staff who will be deeply missed.
“We cannot say more as we are working closely with the police on their ongoing investigation into this incident.”
A post-mortem examination is due to take place at Croydon Mortuary on Saturday.
Police say they are not looking for anyone else in connection with the killing and are appealing for anyone with information to come forward.