At the sounding of the quarter-time siren and with Fremantle holding a 42-point lead, Voss rubbed Petty's hair condescendingly three times as the pair engaged in a back-and-forth verbal.
Melbourne skipper Max Gawn came in to remonstrate with Voss, with the Fremantle forward then making a 'cry baby' gesture at Petty.
The AFL match review panel made its stance clear on Sunday when it handed down a $1500 fine to Voss, which can be reduced to $1000 with an early guilty plea.
It was put under the 'Other Misconduct' category, and makes it clear similar taunts won't be accepted.
Petty has been a target of similar gestures or sledges over the years.
In 2022, he was brought to tears when Brisbane Lions veteran Dayne Zorko sledged him about an ill family member.
Zorko later apologised.
In 2024, Lions defender Noah Answerth directed a cry-baby taunt towards Petty.
Voss became the latest player to target Petty, with North Melbourne great David King labelling the spearhead's actions a "step too far".
"You can embarrass them in the way you play but you can't humiliate them face-to-face," King told Fox Footy.
"I think it's a bad look and I don't think the AFL will be thrilled with this. I think the taunting rule will come into effect. It's an ugly part of our game we don't need."
Voss tried to play down the incident after the game.
"There were a few words being said, but yeah, shake hands at the end of the day," Voss told Fox Sports.
"Probably early in my career I stepped over the line a few times, and as I've matured I've found the line fairly well, and I think I'm in a pretty good space at the moment."
Fremantle coach Justin Longmuir was unaware of the exact details or context behind the incident.
But he praised Voss for the general energy and enthusiasm he brought to the side.
"We understand he treads a fine line at times, and he's got to manage that," Longmuir said.
"But he just brings so much energy to the group that we all buzz off it."
Voss had a more light-hearted moment late in the game when he lifted Ed Langdon over his shoulder and walked six steps to carry his opponent over the boundary line.
The pair had a laugh about that incident, but Voss's taunt on Petty was deemed no laughing matter.Â
Voss kicked 1.2 from 12 disposals in the 17.16 (118) to 10.10 (70) win over Melbourne, and looms as a key player in Fremantle's bid to win their maiden flag.
