(Reuters) - A man who was convicted of stalking and threatening pop star Madonna in the 1990s walked away unnoticed from the California mental health facility where he was being held and remains at large, Los Angeles police said on Thursday.

Robert Dewey Hoskins, 54, was sentenced to 10 years behind bars in 1996 after being arrested for scaling a wall around the singer's home in the Hollywood Hills and threatening to slit her throat.

Madonna testified during Hoskins' trial that she had nightmares about the homeless man from Oregon after seeing him near her home in 1995. She said her bodyguard told her Hoskins claimed she was supposed to be his wife, and "if he couldn't have me, he was going to slice my throat from ear to ear."

While Madonna was away from her home and in Florida later that year, he scaled the perimeter wall there, jumped into her pool and was eventually shot twice by a security guard.

Upon his release from prison, Hoskins was sent to a California hospital. He was eventually let go but was arrested again in July 2011 and sent to a different health facility in the Los Angeles-area community of Norwalk.

Hoskins walked off undetected from that hospital last Friday and has not been seen since. Police describe him as highly psychotic with violent tendencies when not taking medication.