A German man was seen atop his roof, a knife in one hand and his wife's head in the other this morning.

The unidentified 32-year-old man allegedly screamed "Allahu Akbar," which means "God is great" in Arabic, before decapitating his wife on the roof of his five-story apartment, according to a translation of the Berliner Morgenpost. Police described the suspect as mentally ill.

Neighbors said the man and his wife were arguing loudly before they were seen on the rooftop. The man reportedly sharpened his knife and then beheaded the victim while she was still alive.

Horrified witnesses saw the man standing at the roof's edge with his wife's head in his hand, according to police reports obtained by the paper. He allegedly threw the head into the courtyard below.

NewsCore reported that the man put up a fight when police arrived, but was eventually subdued.

Six children, aged 18 months to 13 years old, were all found safe inside the apartment. It's yet unclear whether they witnessed the attack.

Neighbors said that the woman had wanted to throw out her husband.