Speaking to the New Zealand Herald at Hamamatsu City's Entetsu department store, Naoki Tani said he rushed to the basement after receiving a frantic call from women working behind the counter on Saturday.
He did not recognise Collins.
"There was a large man standing behind the counter. I asked him if he was okay and reached out my arm towards him. He suddenly pulled a knife from his right pocket and placed it on the box on the counter. It was a kitchen knife.
"Then he reached into his other pocket and pulled out a large survival knife from his left pocket and put that down on the box as well.
"It was a survival-style knife and had a long curved blade.
"It was very large and the end of it was serrated."
It had previously been reported that Collins was arrested after producing one knife, 17cm long.
Mr Tani said he quickly took the knives and hid them on the other side of the counter, then called the police.
Collins didn't do anything violent, but was behaving in a bizarre way, pacing backwards and forwards behind the counter, rummaging around and saying random words in Japanese which made no sense.
'He kept saying the word shinkansen (bullet train) and abunai (danger).
Mr Tani said one of the staff then brought him a glass of water and he drank it quickly.
"Then he said in Japanese 'One more water please'. It was the only thing he said in Japanese which made any sense."
Collins is expected to be kept at the Hamamatsu Chuo police station for at least another eight days.
- Simon Scott in Hamamatsu City
