The finger pointing was threatening "and made Cr Garey fear Cr Vandervis may strike her".
"The behaviour was highly unprofessional and threatening and affected Cr Garey's perception of her safety in her working environment. It is likely to bring Cr Vandervis and the council into disrepute."
Vandervis objected to Dyhrberg's appointment, and did not take part in the investigation.
He will have a chance to defend himself at a meeting on Tuesday next week, when councillors will decide if they agree he breached the code and, if so, what sanctions he should face.
Possible penalties include suspension from committees, removal of council-funded privileges, a vote of no confidence or being asked to consider resigning.
Dyhrberg also found an emailed apology by Vandervis was weak.
Councillors Garey, Marie Laufiso and Steve Walker made formal complaints on July 29, the day after the meeting, alleging Vandervis yelled at Garey.
Walker stepped in to protect Garey, the investigation noted.
It happened
after Garey ruled against Vandervis on a point of order. He confronted her afterwards.
The deputy mayor told Dyhrberg that Vandervis shouted at her and it escalated to yelling.
Garey labelled the behaviour bullying.
She believed she said something like "don't you point your finger at me", because he replied as he walked away, "I'll point my finger at anyone I want".
Though shaken, she said she was not afraid of Vandervis and felt she had to stand up to him.
"I am extremely concerned that this was not a one-off, but a pattern of behaviour I have observed over several years," she said in her complaint.
Walker said Vandervis was "screaming and yelling". It was an over-the-top "tirade".
Vandervis was "red faced and almost spitting", Walker said in his account.
Walker described it as "horrid male aggression".
Laufiso said the faces of Garey and Vandervis were about 20cm apart.
She described Vandervis' behaviour as bullying and disrespectful.
The Dunedin City Council has kept a file on Vandervis since 2012 and it lists 27 recorded incidents.
They range from claims of swearing and bullying to spraying saliva.
Vandervis rejected the file as "manufactured rubbish".
Vandervis is in his fifth term on the council. He was a close second to Dunedin Mayor Aaron Hawkins in last year's mayoralty race.
In his apology, Vandervis said he had not intended to make a scene and he was sorry about his "loudness".
In future, he would make complaints in writing, he said.
