A man shot dead at a karaoke building in Tokyo's Kabukicho entertainment district was a Korean national who used to be a gangster in Japan, police said Tuesday.

Lee Hung Jong, a 65-year-old Tokyo resident, was a member of a group under the Sumiyoshikai crime syndicate more than 20 years ago, according to the police. Lee sustained three gunshot wounds and was found collapsed Monday afternoon inside the karaoke establishment, which houses many closed rooms for people to sing inside.

The suspected attacker, who is also thought to have gangster links, fled from the scene on a motorcycle, the police said. They suspect it was a premeditated attack resulting from personal trouble between them.

The police have found what they believe was the motorcycle used by the suspect along with a helmet and a cap on a street not far from the crime scene and began investigating surveillance camera footage in the area.

The karaoke box in the center of Kabukicho in Shinjuku Ward is located about 500 meters northeast of JR Shinjuku Station. A number of yakuza gangsters are based in the largely commercial area which is also popular among foreign visitors.

The police received an emergency call from a worker at the karaoke box around 6:30 p.m. Monday, reporting gunshots had been heard and a man was lying bleeding inside the building.

The man was found face down in front of an elevator on the fourth floor. He was taken to a hospital where he was confirmed as deceased.

The police believe the man was shot in a room on the fifth floor, as they found spent bullet casings there. They also found traces of blood stains on an external staircase of the building. The gun has not been found.