Frankie Muniz put a gun to his head and punched his girlfriend during a nuclear domestic argument Friday night ... this according to the woman.
TMZ obtained a police report filed in Phoenix, AZ last Friday. According to the report, Muniz and his girlfriend, Elycia Turnbow, were arguing in their home about "prior relationships." Elycia told cops, Frankie "grabbed a gun and held it to his head, possibly with the intent of committing suicide."
Elycia says she became worried and called one of Frankie's bandmates to take him to the hospital.
Frankie tells a different story, claiming Elycia was screaming and yelling at him when he "fell and hit his head." Muniz says that's why he went to the hospital. Muniz denied putting a gun to his head, but did say, "I grabbed the case, but not the gun ... it isn't even loaded."
In fact ... the cops did find the gun and it was loaded.
Muniz was released a short time later, went home, and just after 10PM the same night, things exploded back at the house. According to the police report, Elycia says, Frankie "punched her in the back of the head, and threw her into a wall while in the downstairs bedroom."
Muniz denied punching Elycia, telling cops, "I love her too much. She is the woman I want to marry."
Muniz told cops ... what actually happened was that he was sleeping but awakened "by Elycia yelling at him and hitting him in the face." Muniz said he was defending himself when "Elycia fell to the ground and started to kick the bedroom door."
Cops say in the report ... there were no visible injuries.
The handgun was impounded and both Frankie and Elycia were warned they'd both go to jail if things got out of control again.