Kirsch, who was best known for his role as Richie Ryan on the Highlander television series, died on Jan. 11 at his residence, according to Los Angeles County Medical Examiner-Coroner records. His manner of death was ruled as a suicide.
A law enforcement source tells ET that EMTs responded to the home but Kirsch was pronounced dead at the scene. He was 51 years old.
Kirsch was a child actor and graduated from Duke University with a degree in political science before returning to acting. He starred in the hit show Highlander from 1992-1997, and while he left the show as a regular cast member in the fifth season, he made an appearance in the series finale episode. He also appeared in a memorable 1995 episode of Friends as a man named Ethan -- who was dating Monica (Courteney Cox) -- in the episode "The One With the Ick Factor." Kirsch's other major television credits include parts in General Hospital, Love Boat: The Next Wave and JAG. He also worked as an acting coach in Los Angeles, and founded his own acting studio called Stan Kirsch Studios.
Highlander's official Facebook page mourned Kirsch's death with a post on Monday.
"Without Stan Kirsch, Highlander: The Series would have been far less," the message reads. "He brought a sense of humor, kindness and youthful enthusiasm to the character of Richie Ryan for six seasons. ... Beyond Highlander: The Series, Stan Kirsch was an accomplished acting coach. We have heard first-hand testimonials from many of his students; all of them having considered Stan an incredible teacher and a gift of a human being."
"Every time we had the opportunity to catch up with Stan, he was nothing but kind, thoughtful and sincere," the post continued. "He was a warm presence that will be missed."
Kirsch is survived by his wife, actress Kristyn Green.
If you or someone you know needs help, please call the National Suicide Prevention Lifeline at 1-800-273-TALK (8255).