Police attempted to negotiate with the gunman but then burst into the building in Yokohama, a city just south of Tokyo, after they lost contact. Inside, they found him dead with a gunshot wound to the head, said police spokesman Shigeki Umehara. Investigators found a revolver at his side, which he apparently used to kill himself, he said.

Police identified the gunman as Kenji Hayashi, a 62-year-old member of the third-largest gangster group in Japan, the Inagawa-kai.

The three wounded men were rushed to a hospital and one was unconscious and in critical condition, according to prefectural police spokesman Katsuzo Nakayama. The two others were conscious.

According to an account from one of the wounded men, Hayashi suddenly pulled out a gun and shot the three while talking inside a real estate agent's office, Umehara said. Police are investigating whether the three wounded men are also gang members.

Guns are strictly controlled in Japan, and shootings are rare, though when they do occur, they are often linked to gangsters, known as yakuza, or Japanese mafia.

Yakuza typically make their income from extortion, gambling, prostitution, gunrunning, drug-trafficking and construction kickback schemes.