In addition to a handgun attached to a cord around his neck, Suzuki reportedly had with him two knives as well as an 18-litre container and two bottles containing an unspecified liquid, according to major media including TV Asahi network.
He also confirmed to police that he was behind the hospital shooting, which resulted in two injuries, and the fire at an apartment where he lived, local media said.
Broadcaster NTV said Suzuki told police he had “shot” a gun at the hospital and “burned my house”.
He told police he “was frustrated” by a meeting with a doctor at the hospital, the Asahi Shimbun said, and had a grudge against the post office over a traffic accident.
The eight-hour post office showdown lasted until after 10pm, with live television pictures showing the building surrounded by police cars with flashing lights.
Crime rates are exceedingly low and gun violence nearly non-existent in Japan, which has some of the toughest firearms laws in the world.
Police finally arrested Suzuki after one of the hostages was released and the other managed to leave the building on her own.