Minutes later, he walked into a dairy in Hillside Rd still wielding the pipe.
Waenga smashed a confectionery display then dropped the weapon and told the shopkeeper to call police.
When arrested, the man said he had "had enough of life".
Judge Kevin Phillips asked him to elaborate on the explanation yesterday.
"I don't have a purpose so I resort to these kind of things. It's not an excuse though," Waenga said.
The court heard there might be a bed at residential rehabilitation facility Moana House but the defendant quickly stymied that plan.
"It's my decision at the end of the day. I don't agree to go," he said. "It's not adequate. It's not suited to me."
A Probation report revealed a little more about Waenga and his unwavering desire to remain behind bars.
It described him as having "personal difficulties" and wanting to remove himself from society.
Prison, the report said, gave Waenga "space" and allowed him to be himself.
Phillips told the self-represented man that there was no other option but imprisonment.
"Whatever, if it's jail it's jail. I just came here to receive my sentence," Waenga said.
The judge imposed a sentence of six months, which means the man will be out again in a matter of weeks.