The star had returned home from his daily game of pickleball and reportedly sent his assistant out on an errand. When they returned two hours later, they found him unresponsive and called the police.
TV presenter Billy Bush has revealed that he spoke to the actor's pickleball partner, who said that he left the game complaining of tiredness.
The presenter shared Matthew's love of the game, writing on Instagram, "He played every day and sometimes twice. It regulated his days.
"I spoke to the woman he played with this morning and every morning. She is in shock, adored Matt…she said he had been fatigued today and over the past week. A little more than usual. He played for one hour then went home."
Billy added that he was grateful to have known Matthew and "admired his courage under the grips of a relentless disease", referencing the star's addiction battle, for which he went to rehab multiple times.
Friends of the star have revealed to Daily Mail that Matthew had been on "good form" and was committed to his sobriety and helping others facing similar issues.
There were no illegal drugs found at the actor's home, however, law enforcement sources told TMZ that multiple prescription drugs were found at his house.
"Authorities found antidepressants, anti-anxiety drugs and a COPD drug in the house," the gossip site claims.
The World Health Organisation states that chronic obstructive pulmonary disease (COPD) is a common lung disease that causes restricted airflow and breathing problems. It is most often caused by smoking and puts sufferers at a higher risk of other health problems.
An autopsy will reveal whether or not any drugs were in his system at the time of his death.
Matthew spoke about his experience with addiction for many years before his passing and wrote about it in his 2022 memoir, Friends, Lovers and the Big Terrible Thing.
He shared how he spent almost $14 million trying to get sober, underwent 14 surgeries and almost died multiple times.
"It is very odd to live in a world where if you died, it would shock people but surprise no one," he wrote, sharing that he "nearly died" at the age of 49 when his colon burst from opioid use.
He revealed to People magazine last year that he was in a coma for two weeks and spent five months in the hospital.
"The doctors told my family that I had a two per cent chance to live," Matthew wrote in his book. "I was put on a thing called an ECMO machine, which does all the breathing for your heart and your lungs. And that’s called a Hail Mary. No one survives that."
He also revealed he was optimistic about his recovery, saying, "I'm pretty healthy now."
The star joked: "I’ve got to not go to the gym much more because I don’t want to only be able to play superheroes."
Matthew didn't tell the publication how long he'd been sober, saying mistakes are part of the journey.
"It’s important, but if you lose your sobriety, it doesn’t mean you lose all that time and education. Your sober date changes, but that’s all. As long as you were able to fight your way back without dying, you learn a lot," he said.
The actor said that despite encountering plenty of dark times, they made him stronger.
"I’m most surprised with my resilience. The way that I can bounce back from all this torture and awfulness," Matthew said at the time.
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