One of the suspects in the killing of a freelance journalist who wrote about Japan's underworld groups allegedly committed the crime because the reporter refused to apologize for criticizing him in publications, police sources said Saturday.

Keizo Sakurai, 42, decided to kill Satoru Someya, 38, in late August after the journalist made critical comments about Sakurai, a locksmith, in his book "Kabukicho Underground," published the previous month, and a magazine article, and refused to apologize, the sources said.

Sakurai contacted a female employee of a restaurant in Tokyo's Toshima Ward frequented by Someya and asked her to call him when the journalist showed up.

On Sept. 6, Sakurai and Yoshihiro Kumamoto, 31, confined Someya to a condo in Shinjuku Ward and demanded an apology but Someya refused, the sources said.

The police allege that Sakurai, Kumamoto and a third suspect identified as Ryoichi Fujii, 34, killed Someya around 11:30 p.m. that day by fatally stabbing him on a boat in Tokyo Bay.