Denise Richards ‘deeply heartbroken’ over Patrick Muldoon’s death

Denise Richards has issued an emotional tribute to her ex-boyfriend Patrick Muldoon, following his tragic death aged 57.

The news broke on Sunday (19 April) that the American actor and producer, who was best known for his roles in Days of Our Lives and the movie Starship Troopers, had passed away suddenly following a heart attack.

It was later confirmed to Deadline that he died at home, where he lived with his partner of two years, Miriam Rothbarth.

Since then, the tributes have been pouring in from the entertainment world and beyond, including from his ex and 'best friend,' Denise Richards.

Richards and Muldoon met in an acting class when she was just 19, and dated for almost five years in the 1990s, before starring in the 2000 movie Starship Troopers together.

They maintained a close friendship and kept in contact throughout the years after their split.

Now, the 55-year-old actress has taken to Instagram to share an emotional video montage featuring pictures of the duo over the years, as well as a heartfelt message.

Denise Richards has paid tribute to Patrick Muldoon after he died suddenly of a heart attack (Jeff Kravitz/Getty Images)

She wrote: "This is so hard for me to put into words. I am deeply heartbroken & devastated losing you. You were my best friend & my family.

"We met in our first acting class, I was 19 never had an acting job and you were 21 a student at USC doing a recurring role on who’s the boss. And here we are. 36 years later.

"My whole adult life & I don’t know it without you. The friendship, love, support, respect & loyalty we had was unconditional and rare. You lit up every room you walked into. You are larger than life & Everyone was drawn to you."

Richards continued: "So talented & most underrated actor. And most humble. Everything you did was infectious. Your laugh, your kindness, your wit, your strength, your loyalty, your passion, and your zest for life.

"We’ve been each other’s rock. Our memories together are endless. You’ve had my back and protected me more than anyone. I don’t know what I’m going to do without you here. You’re my voice of reason & pillar of strength. "Especially during this last year of pain & heartache. And now I need you more than ever, for this pain and heartache losing you. "

She shared a montage of pictures taken throughout their friendship (Instagram/deniserichards)

Using her nickname for him, she emotionally concluded: "Schweetbabe we’ve had those conversations.. We thought we’d live forever or at least into our 90’s. Schweetbabe I will be looking for those signs. I need to know you’re still here with me. I love you so much & miss you dearly schweetbabe."

Muldoon was best known for playing Austin Reed in the 1990s sitcom Days of Our Lives, as well as for his role another popular drama, Melrose Place.

His last big movie appearance is still yet to air, in the crime thriller Dirty Hands, which is set to be released in just days on 24 April. He starred alongside Richards in the movie.