Arber Bako, the man who opened fire on a bar in Mikrolimano last month, injuring more than 10 people, admitted on Tuesday to taking part in another attack that led to one man being killed, sources said.
Bako appeared before a prosecutor to give his deposition after being arrested last week.
Speaking through an interpreter and with no defense lawyer, Bako said that he suffers from mental problems and is an alcoholic.
He asked to be examined by a psychologist.
Before being remanded in custody, the Albanian national said that he was involved in a shooting at a bar in Metaxourgeio on October 31, when a 43-year-old man was killed.
Bako claimed that another man also took part in the shooting and that he had not intended to kill his victim.
Ballistic tests showed that a Kalashnikov assault rifle fished out of the water at Piraeus port on Monday had been used in the Metaxourgeio shooting.
It had also been fired on two other occasions in October, in an armed robbery in Omonia and during an incident in Aghios Panteleimonas, but not at the bar in Mikrolimano.