The 29-year-old was arrested on Wednesday and admitted to the crime of shooting his former girlfriend in the head, Berlin prosecutors said.
A day later a 39-year-old accomplice was also arrested and has since admitted his involvement.
The arrests came after a 25-year-old Polish woman was found unconscious on a street in the Neukölln neighbourhood on December 27th.
The woman had been shot in the head on Oderstraße, a street adjacent to the popular Tempelhofer Feld park. A passerby found her lying in the entrance to a courtyard slightly before midnight. Emergency services rushed her to hospital where she underwent emergency surgery, but she died later in the night.
Investigators believe that the ex-boyfriend fired the fatal shot.
Neukölln is a sought after address for young expatriates working in Berlin’s creative industries. As well as hosting a large population of educated young migrants who hang out in its hip bars and cafes, Neukölln is known for organized criminality and often makes headlines as a hotspot for violent crime.