A man believed to be responsible for the 1991 rape and strangling of a 14-year-old girl killed himself in prison hours after investigators told him DNA evidence linked him to the unsolved case, authorities said Monday.

Derick Moncada, 35, was serving time at Kern Valley State Prison for threatening his girlfriend, beating a former girlfriend and leading police on a chase when Alameda County sheriff's deputies went to question him last week about Jessica McHenry's killing.

The girl's burned body was found naked from the waist down in a ditch along a rural road in Livermore, about 40 miles east of San Francisco. She was last seen alive walking home from Granada High School earlier in the day.

Alameda County Sheriff's Sgt. Scott Dudek said the March 12 interview began cordially, but quickly changed when investigators asked Moncada if he knew Jessica.

"He never admitted anything," Dudek said, adding the interview ended when Moncada asked for a lawyer.

About five months earlier, investigators learned that Moncada's DNA matched samples taken from Jessica's body. Results from a second sample taken from Moncada last week were pending, but Dudek said that test was a formality and authorities were certain Moncada was the killer.

Eight hours later, Moncada was found hanging in his cell, Dudek said. He left behind a suicide note, professing his innocence, apologizing to his family for sullying the family name and pledging "death before dishonor," Dudek said.

A call to the Department of Corrections and Rehabilitation was not immediately returned.