Petty had to spend time off the field after breaking down during the three-quarter break as the Demons moved into the box seat for a top-two finish with a dominant 18.7 (115) to 8.9 (57) victory.
Zorko was confronted by several Demons after the final siren before having a long discussion with Petty on the field.
Demons coach Simon Goodwin confirmed 22-year-old Petty had heard something personal said about a family member and the Lions had been "apologetic" towards the Demons about the incident.
"Obviously, Petts thought he heard something inappropriate about a family member, he was a bit upset about it," Goodwin said.
"The Lions have spoken to us and obviously the AFL will look at it, but that's pretty much the details we can give at the moment.
"Brisbane have been quite apologetic towards us, and that's the type of footy club they are ... we'll take them at their word."
Lions coach Chris Fagan said he was unaware of the exact nature of the incident but admitted he'd be disappointed if his captain had overstepped the mark.
"It would concern me that any of our players got caught up in an incident like that, but I won't judge just yet because I don't know enough about it," Fagan said.
The incident stole the attention away from a magnificent Demons' display as they battered Brisbane with a free-scoring first half.
In-form Kysaiah Pickett kicked four goals, while Bayley Fritsch also scored four, with Ben Brown booting three majors.
Christian Petracca dominated with a game-high 10 score involvements as well as 23 disposals, five inside 50s and two goals while Clayton Oliver (30 disposals) and Angus Brayshaw (27 touches) were also highly influential.
There was a late concern for the Demons, however, with Luke Jackson subbed out in the final term with a corked calf but Goodwin was confident it wouldn't be a concern for finals.
Joe Daniher and Hugh McCluggage kicked two goals each for the Lions while Lachie Neale was valiant in defeat with 29 disposals, six tackles and four clearances.
Adding to Brisbane's woes, Cam Rayner was placed on report in the first quarter for a sling tackle on Brown which left the Demon needing treatment for a bloodied nose.
Midfielder Jarrod Berry was also subbed out in the final quarter after succumbing to an ankle injury picked up earlier in the match.
In front of a sellout Friday night crowd of 32,172, the Demons set the template when Pickett kicked his first goal just 20 seconds into the match.
Melbourne had three goals on the board and were 20 points clear when a Daniher long bomb finally got the hosts on the board 13 minutes in.
Down by 31 at the first turn, Brisbane kicked the first goal of the second quarter through Dan McStay but from there it was all one-way traffic as the Demons kicked seven unanswered goals.
The fortunes of the two teams were highlighted when a hopeful kick by Petracca took a wicked bounce over a Lions defender and over the goal-line in the rout.
By halftime the Demons had charged to an unassailable 66-point advantage.
Melbourne's 13.3 scoreline was the highest conceded at halftime by the Lions at the Gabba since Geelong's 15.6 on their way to an 85-point win in round 16, 2017.
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