The 43-year-old producer feuded with Baldwin in a series of tweets Wednesday after claiming the 59-year-old actor was aware Reed was 16 years old while filming the 2006 movie.
"Really, are you going to continue to deny that you didn't know she was 16?? I'll bury you," Brunetti tweeted.
"I was told she was 16 by her hairdresser. At the end of the shoot. You're already buried," Baldwin responded.
"You're a fool. She just came off a movie called 13!! Do I need to bring in the other crew to vouch that you knew?? @NickGuthe wanna weigh in," Brunetti wrote.
"Only a Hollywood idiot like u would suggest that a film title is a birth certificate," Baldwin shot back.
Brunetti initially called out Baldwin after the actor released his memoir, Nevertheless, on Tuesday. Baldwin claimed in the book that Brunetti and other Mini's First Time producers misled him about Reed, with whom he shares sex scenes in the film.
"I was forty-seven, and it never occurred to me to ask how old Nikki Reed was. When I found out, just as we finished, that she was seventeen, I flipped out on the producers, who had told me something different," the actor said.
Brunetti, who is known for the Fifty Shades movies, told The Hollywood Reporter Baldwin lied in the memoir and was aware of Reed's age "before [they] even cast the movie." He also slammed the actor on Twitter.
"My first indie film was Mini's starring @AlecBaldwin who knew @NikkiReed_I_Am was 16 (not 17) and he didn't mind," the producer wrote.
"If @AlecBaldwin had simply said in his book he didn't know @NikkiReed_I_Am's age, I would let it go," he added. "However to say that when he found out after filming he yelled at the producers (I being 1 on the film) makes it out to seem we did wrong."