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.
Petty has been a target of similar gestures or sledges over the years.
In 2022, Petty was brought to tears when Brisbane Lions veteran Dayne Zorko sledged him about a sick family member.
Zorko later apologised for that incident.
Then 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.
"I'm not sure whether there's anything in the rules you could sanction the player, but it's a worthy discussion because in the end it's an ugly part of our game we don't need."
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 brings 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.
"He plays with great energy. He tries to help his teammates out who are getting tagged. He goes after target players for us or players we want to try and negate from the opposition.
"So he does a lot right in that sense."
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 it's Voss' taunt on Petty that will dominate the headlines and spark debate about whether the AFL need to create new rules to clamp down on the issue.
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.
