Eastern city of Potsdam’s police say 51-year-old employee arrested “under strong suspicion” of carrying out the assault in which at least four people were killed and one was injured.
Four people have been killed and one person seriously wounded in an attack at a care clinic in Germany.
Brandenburg police said on Thursday the victims were subjected to "intense, extreme violence" but did not give any details around the circumstances of the killings in eastern city of Potsdam.
A 51-year-old employee has been arrested "under strong suspicion" of carrying out the assault, police said.
The motivation for the attack is not known, they added.
Those killed are believed to be patients at the clinic, local newspaper Potsdamer Neueste Nachrichten reported.
Brandenburg state police were called to Oberlin Clinic at around 9 pm local time (1900 GMT) on Wednesday, according to reports, with the victims later discovered in their rooms.
Police have also imposed a news blackout.
The clinic specialises in helping those with disabilities, offering live-in care. The site includes housing, schools, and workshops.