Gunnar Hansen -- who terrorized actress Marilyn Burns as Leatherface in the original "Texas Chainsaw Massacre" -- says Burns appeared skinny and frail in recent years ... and appeared to be in declining health before her death.
Hansen tells TMZ ... he and Burns remained close after the 1974 horror flick, and says her health issues were obvious to him in the last few years. But he adds, they never discussed any specific ailment.
TMZ broke the story ... the 65-year-old Burns was found dead Tuesday at her home in Houston. An autopsy is being conducted to determine cause of death.
Hansen -- who continues to act in slasher/horror flicks -- says he spoke to Burns once a month and would visit her at home -- calling her a wonderful woman who was humorous and generous.
He says he and other actors from the original film -- including Allen Danziger and Ed Neal -- are making arrangements to attend Burns' funeral.