Convicted killer Michael Johnson used "some sort of metal blade or razor to cut his right jugular vein and an artery inside his right elbow," a Texas Department of Criminal Justice news release said.
Johnson, 29, was scheduled to die by lethal injection at 6 p.m. in Huntsville, Texas, but apparently killed himself at 2:45 a.m., the Waco (Texas) Tribune-Herald reported.
The news release said death row inmates are checked every 15 minutes, and that Johnson had spoken with guards at 2:30 and "made no indications that he was contemplating suicide, nor has a note or other explanation been found."
Johnson was sentenced to death in 1996 by a Waco jury for the September 1995 shooting death of a convenience store worker during a robbery attempt.
The state Office of Inspector General is investigating, the report said.
Aaron Carter is still in love with Hilary Duff
NBC reportedly holds celebs hostage to Jimmy Fallon's show