Megan Fox is drawing a line in the sand.
Nearly a year has passed since the actress and Brian Austin Green called it quits, but the former couple is still struggling to keep the peace. After Megan decided to make their private turmoil public by calling out her estranged husband on Instagram this past weekend, a source tells E! News exclusively that tension between the pair was building for quite some time.
"She reached her breaking point and has had enough of Brian's games," the insider explains. "She is incredibly frustrated that he's trying to make her look like a bad mom and decided to call him out on it. She especially hates that he's using the kids to try and get back at her."
In the comments section of a since-deleted photo of the Beverly Hills, 90210 actor alongside their 4-year-old son Journey dressed in Halloween costumes, Megan called Brian "so intoxicated with feeding the pervasive narrative that I'm an absent mother."
"I had a great halloween with them yesterday," she wrote, "and yet notice how absent they are from my social media. I know you love your kids. But I don't know why you can't stop using them to posture via Instagram."
According to our source, Brian is "bitter" about the end of their marriage and "constantly trying to get under her skin to get some sort of attention or reaction."
As for why Megan felt it was necessary to air their dirty laundry for all to see, the insider adds, "She feels like he crossed a line and that something needed to be said publicly so that maybe he will think about what he's doing."
Brian has yet to address Megan's commentary, however it could only be a matter of time before the father of four takes to his podcast with his side of the story. In August, Brian spoke candidly about adjusting to co-parenting.
"There's no rule book to it," he remarked at the time. "There's no way of doing it right or doing it wrong. We're learning as we go. The important thing for us is just communicating as much as we can."
The 47-year-old continued, "I wish Megan the absolute best in everything. I want her to be completely happy for her and for the kids. That's super important."
Brian's efforts have apparently fallen short, especially as other women close to the star speak out in defense of Megan.
Ex-wife Vanessa Marcil, who shares 18-year-old son Kassius with Brian, wrote on Instagram, "The truth always comes out in the end," adding, "#ImWithYouSister."
Model Courtney Stodden, who was romantically linked to Brian following his split from Megan, said she's "proud" of the Transformers star for speaking up.
"During my time spent with him, when I was over at his house, his kids were never there," Courtney claimed in a lengthy Instagram statement on Nov. 2. "They were always with Megan. She wasn't an absent mother. And yet, like she says - she doesn't plaster them all over her social."
"There were times Brian would tell me that he couldn't see me because he had his kids - and I later found out that this wasn't true, he was actually just seeing other women at those times," she added, further alleging that Brian posted photos of his children to "protect his image" as a "doting single dad."
"The whole experience was a bit gross," Courtney concluded. "Women and children are not props. How long until men realize this?"
E! News reached out to reps for Megan and Brian for comment.