As well as allegedly sending highly offensive packages to the two men - one containing a headless rat inscribed with the message "jilted lover" - Tucker was accused of sending obscene letters and emails, including defamatory statements about his former employer and homophobic slurs.
The offending was alleged to have occurred in 2014 and 2015, after Tucker left Custom.
In a just-released decision the tribunal ruled the two charges were proven against Tucker, amounting to disgraceful misconduct.
Tucker, who now owns Netrealty and represented himself during the hearing, was discharged without conviction last year in Auckland District Court after he admitted sending a package containing what was believed to be human excrement and broken glass to Beard.
Beard told the hearing he began opening the courier-type package "but as I started I smelled something vile".
He took it to police and opened it outside with an officer using protective gloves.
"Inside was what looked and smelled like human faeces. I was gagging over the side of Auckland Central Police Station."
Tucker argued the package was first sent to him and he was simply returning it.
But he "vehemently denied" sending a further series of packages to Wills and Beard, including the decapitated rodent, which leaked brown liquid over a Custom staff member's dress.
"He said he was a life member of the SPCA, and found what had been done to the animal abhorrent," the decision says.
"Mr Tucker suggested Mr Wills had sent the package to the agency himself."
Tucker did accept leaving a derogatory voice message on Wills' phone, referring to his old boss as a "c**k-sucking f*****t".
But he claimed he was stressed at the time, having been pepper-sprayed by his former partner that day, who had then tried to "frame him as the attacker" when police were involved, the decision says.
He denied verbally abusing Wills in Ponsonby in March last year by saying, "Found your balls yet you gutless piece of shit", though the tribunal ruled this did occur.
The tribunal also ruled Tucker had sent a series of anonymous letters to Custom clients, bad-mouthing the firm with disparaging claims about its ethics and sales record.
Allegations he had vandalised Custom signs and egged a staff member's car were not proven.
"The tribunal does not accept Mr Tucker's submissions but even if they were to be accepted, that does not excuse his conduct."
It found Tucker's actions "would reasonably be regarded by agents of good standing, or reasonable members of the public, as disgraceful".
The matter will now go to a penalty hearing when Tucker could potentially lose his licence.
Speaking today, Tucker said he planned to appeal the tribunal's ruling to the High Court.
He maintained the complaints against him were without merit and said he had practised real estate with honesty and integrity for 20 years and was still working in the industry.
"It's quite difficult at the moment, but I do have some loyal clients who have stuck by me."
