Kevin Winter/Getty Images Ray Fisher and Jason Momoa
Momoa, 41, shared a photo of himself and Fisher, 33, on his Instagram account on Monday, writing, "THIS S— HAS TO STOP AND NEEDS TO BE LOOKED AT. @ray8fisher AND EVERYONE ELSE WHO EXPERIENCED WHAT HAPPEN UNDER THE WATCH OF @wbpictures NEEDS PROPER INVESTIGATION."
The Aquaman star then said the announcement that he was in talks to voice Frosty the Snowman in an upcoming movie was "fake." According to Variety, the announcement was released on July 1, the same day Fisher came forward with his allegations of mistreatment by director Joss Whedon.
“I just think it’s f— up that people released a fake Frosty announcement without my permission to try to distract from Ray Fisher speaking up about the s— way we were treated on Justice League reshoots," Momoa wrote. "Serious stuff went down. It needs to be investigated and people need to be held accountable. #IStandWithRayFisher. aloha j."
Fisher commented on Momoa's post with, "🙌🏽You already know bro! 🙌🏽A>E🔱+🦾."
Warner Bros. did not immediately respond to PEOPLE’s request for comment.
On Monday, Fisher tweeted about the investigation being conducted by Warner Bros. in regards to the allegations he had made.
“To-date, the 'independent' firm hired by @wbpictures has conveniently avoided contacting key witnesses who gave damning statements to WB HR," Fisher tweeted. "They’ve also started interviews with (and have since ghosted) witnesses that have implicated former and current top level executives."
Others (including an implicated individual that called me to apologize) have already been interviewed.— Ray Fisher (@ray8fisher) September 14, 2020
We will not let ANY investigator cherry-pick interviewees that best suit @wbpictures’ false narrative and scapegoating efforts.
All with stories WILL be heard!
In a second tweet, he added, "Others (including an implicated individual that called me to apologize) have already been interviewed. We will not let ANY investigator cherry-pick interviewees that best suit @wbpictures’ false narrative and scapegoating efforts. All with stories WILL be heard! A>E."
In July, Fisher claimed Whedon "was gross, abusive, unprofessional, and completely unacceptable," while working on the 2017 action film, adding the director "was enabled, in many ways, by Geoff Johns and Jon Berg."
Johns is an American comic book writer who served as the President and Chief Creative Officer of DC Entertainment from 2016 to 2018, while Justice League was being made. Berg was a producer for the film.
Earlier this month, Warner Bros. defended its executives in a statement obtained by Entertainment Weekly.
"In July, Ray Fisher's representatives asked DC Films President Walter Hamada to talk to Mr. Fisher about his concerns during the production of Justice League," the statement read. "The two had previously spoken when Mr. Hamada asked him to reprise his role as Cyborg in Warner Bros.' upcoming Flash movie, together with other members of the Justice League."
"In their July conversation, Mr. Fisher recounted disagreements he'd had with the film's creative team regarding his portrayal of Cyborg, and complained that his suggested script revisions were not adopted," the statement continued. "Mr. Hamada explained that creative differences are a normal part of the production process, and that a film's writer/director ultimately has to be in charge of these matters."
The statement also addressed Fisher's update on Twitter at the time, in which he said he "received a phone call from the President of DC Films wherein he attempted to throw Joss Whedon and Jon Berg under the bus in hopes that I would relent on Geoff Johns." Fisher added, "I will not."
"Notably, Mr. Hamada also told Mr. Fisher that he would elevate his concerns to WarnerMedia so they could conduct an investigation. At no time did Mr. Hamada ever 'throw anyone under the bus,' as Mr. Fisher has falsely claimed, or render any judgments about the Justice League production, in which Mr. Hamada had no involvement, since filming occurred before Mr. Hamada was elevated to his current position," the statement from Warner Bros said.
The statement went on to claim Fisher "never alleged any actionable misconduct against him" and "declined to speak to the investigator" hired to look into his claims.
Fisher disputed the Warner Bros. statement, tweeting the studio's statement is a "desperate and scattershot attempt to discredit me to continue protecting those in power." He noted that he met with an investigator via Zoom on Aug. 26. and shared a screenshot of an email he sent to his team following the meeting.
"It’s also worth noting that I made it clear to the world on Aug 21st that I would be vetting the investigator to ensure a fair and protected process for all witnesses," Fisher continued in another Tweet, adding that Warner Bros. "has escalated this to an entirely different level, but I’m ready to meet the challenge."
A representative for Fisher has not responded to PEOPLE’s request for comment.
Momoa and Fisher will be seen in Zach Snyder's version of Justice League, titled Zack Snyder's Justice League. The film will also star Ben Affleck, Henry Cavill, Gal Gadot and Ezra Miller.
Zack Snyder's Justice League will debut on HBO Max in 2021.