The former star of US soaps Days Of Our Lives and Melrose Place passed away "suddenly" on Sunday morning aged 57, according to Deadline.com, with the publication reporting he suffered a heart attack.
The news comes just two days after Muldoon took to Instagram to tell fans he had landed a role producing new movie Kockroach starring Chris Hemsworth, Channing Tatum and Taron Egerton and the movie would be filming in Australia.
He wrote: "So excited to be a part of this amazing project KOCKROACH directed by Matt Ross starring Chris Hemsworth, Taron Edgerton, Zazzie Beetz And Alec Baldwin.
"Filming now in Australia @chrishemsworth @taron.egerton @zaziebeetz #tarinedgerton #chrishemsworth #mattross #producer."
Muldoon grew up in California and started acting in college, landing a role in sitcom Who's The Boss? and appearing in teen show Saved By The Bell for three episodes shortly after he graduated in 1991.
Muldoon went on to land his role as Austin Reed on hit soap Days of Our Lives, staying with the show between 1992 and 1995 and returning for a second stint from 2011 until 2012.
In the mid-1990s he went on to star in Melrose Place as villain Richard Hart from 1995 until 1996.
He scored numerous movie roles over the years appearing as Zander Barcalow in Starship Troopers in 1997 and landing a role in 1999's Stigmata while more recently he appeared in Deadlock in 2021 with Bruce Willis and in 2022 Liam Neeson film Marlowe, with Muldoon also working as a producer on the film.
His latest movie Dirty Hands was due to be released later in 2026.
Muldoon is survived by his partner, Miriam Rothbart and his parents, Deanna and Patrick Muldoon Sr.
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