Bryan Kohberger butchered the face of Kaylee Goncalves because she screwed up his plans to rape one of his other victims, Maddie Mogen, according to a retired FBI agent.

TMZ interviewed former fed Jennifer Coffindaffer, who has long studied and been a media consultant on the Kohberger case — and she’s now sharing with TMZ her horrific theory of the convicted killer’s motive.

Coffindaffer tells TMZ … Kohberger broke into the house in Moscow, Idaho, that fateful night in November 2022 to forcibly rape Mogen in her bed on the third floor.

She says Kohberger’s plan was derailed after he stepped inside Mogen’s room only to find her sleeping in bed with Goncalves, one of her roommates.

Coffindaffer says Mogen was Kohberger’s target because he went straight to her room, but he got pissed when he saw Goncalves there, making it virtually impossible for him to fulfill his twisted sexual desires.

As a result, Kohberger took out his rage on Goncalves, stabbing her more than 20 times in the face until she was unrecognizable, and also strangling her … according to Coffindaffer, citing the autopsy report.

Coffindaffer also said Kohberger killed Mogen by slicing open her chest before murdering two more victims, Xana Kernodle, and her boyfriend, Ethan Chapin.

The former FBI agent adds, “Kaylee ruined his plans on how the night would go, that’s why her face was completely disfigured.”