Auckland lawyer Matthew Piper, who helped pull the man to safety, said he was struggling "almost like a fish".
"He was twitching and still trying to call things out. It was kind of babble. He continued to struggle after he was pulled back over and was making noises about various injustices, no one could really understand him."
Others in the public gallery said the man had shouted words including "Work and Income," "oppression" and "John Key" before he tried to jump.
The security guard who first reached the man later received medical treatment for suspected cracked ribs.
The incident sparked a fiery exchange between Labour and National MPs.
Labour MPs were outraged by Prime Minister John Key's reaction, saying he shouted out "You should be ashamed of yourselves. That's down to you."
Mr Goff said the clear implication from Mr Key was that he thought it was a Labour Party stunt.
Mr Key had used the case of a "sad situation of a guy who has mental health problems and laid the blame for that on the Labour Party as if we had instigated the action. It's a disgrace he could even have made that allegation", Mr Goff said.
A spokeswoman for the Prime Minister later said his comments related to Labour's criticism of Mr Key's security.
"The Prime Minister's comments following the incident were a reflection on the Labour Party's continued criticism of his DPS security detail - which included criticism of his being accompanied inside the parliamentary complex. It should be noted a DPS member was involved in restraining the member of the public."
- with APNZ