A male psychiatric patient is being questioned in connection with a series of incidents which left one patient dead, another seriously injured and a staff member also injured yesterday.
The incident happened at about 7pm at St Otteran's Hospital on John's Hill in Waterford city.
A female patient was fatally injured in a stabbing while another female patient was seriously injured.
The dead woman has been named by gardaí as Marie O’Brien (54), a single woman from Waterford city. Family members have been informed of the tragedy.
A staff member suffered a slash injury to the face.
Shortly afterwards, a man was arrested and taken to Waterford Garda station where he remains in custody.
Gardaí said both the deceased and the suspect were patients at St Otteran’s.
It is understood the incident started indoors, in the hospital’s rehabilitation unit, but concluded outside in the grounds.
It is also understood that the weapon used in the assaults was a knife.
The scene has been preserved by gardai overnight pending a full technical examination this morning.
Meanwhile, a postmortem examination on the dead woman's remains will be carried today at Waterford Regional Hospital.
Gardaí last night interviewed other patients as well as staff at St Otteran’s Hospital.
In a statement, the HSE confirmed that “an incident has occurred within the Community Mental Health Services in Waterford”.
The incident is now “the subject of a Garda investigation and the HSE will undertake its own review,” the statement said. “HSE wishes to offer its sincere condolences to the family of the deceased.”