A Texas man posted a photo of his dead girlfriend’s body on her Facebook page on Sunday after fatally stabbing her as part of a suicide pact, the police say. The image remained on the site for 36 hours before Facebook removed it.

The man, Kenneth Alan Amyx, 45, told the authorities that he and his girlfriend, Jennifer Streit-Spears, 43, had discussed a suicide pact for months. They had been drinking at an apartment in Plano, Tex., and had agreed to stab each other until both died, according to a Plano Police Department affidavit. But Ms. Streit-Spears “chickened out,” Mr. Amyx said, and he had to “finish her off,” according to the affidavit.

Officer David Tilley, a spokesman for the department, said that Mr. Amyx not only posted a photo of Ms. Streit-Spears — nude and with her neck cut — on her page, he also posted a selfie of his face covered in blood and the words “Pray for us,” the officer said.

Officer Tilley said the photo of the body was dark, as though the lights had been out and the photo had been taken without a flash. Still, he said, “it was quite disturbing.”