A nurse has been stabbed to death at a mental hospital in London
He died at the scene on Thursday afternoon and has not yet been formally identified by police.
A 40-year-old man, who police believe was a patient at the hospital, was arrested at the scene on suspicion of murder.
He is currently being treated at another hospital in south London for an injury to his hand.
A Metropolitan Police spokesman said: "We retain an open mind relating to the circumstances surrounding the incident."
The private hospital, in Brighton Road, provides treatment and rehabilitation for adults with long-term mental health problems.
It offers residential care for up to 25 patients, including those who have been detained under the Mental Health Act.
A 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.
Any witnesses can call police on 101 or Crimestoppers anonymously on 0800 555111.