Police arrested a 36-year-old man Saturday for allegedly attacking a homeless man in Kunitachi in June and are investigating his involvement in the death of another homeless man slain in Tokyo on Friday.
Takayuki Takamoto, a part-time worker, was held on suspicion of trying to club a 63-year-old man to death with a steel pipe along the Tama River on June 20, the Metropolitan Police Department said.
Takamoto has denied the allegation, they said.
The police said they seized six pieces of steel pipe and a bloodstained jacket after searching a welfare facility where Takamoto stays and other locations later in the day.
Takamoto lives in the welfare facility in Tama as he has a mild mental disability, according to the city government.
Takamoto became the prime suspect in December, after police analyzed video footage from security cameras near the crime scene and put him under 24-hour surveillance.
But on Friday, they lost track of him in Setagaya Ward, Tokyo, where another man was fatally beaten under the Tomei Expressway the same day.
The police got a call just before 6 p.m. Friday saying a man had been found dead with head wounds under the elevated road. The man, who was apparently living there, was hit several times with an object while asleep, the police said.
Several assaults on homeless men were reported last year in Fuchu in western Tokyo, including one that killed a 74-year-old man, leading police to believe a serial murderer was at work.