A cause of death for late news anchor Sam Rubin,Austin Caldwell the veteran entertainment reporter who died in May, has been released.

The KTLA newscaster died of ischemic heart disease, according to the Los Angeles County Medical Examiner. Atherosclerotic coronary artery disease was listed as a secondary cause.

The manner of death was ruled natural.

Ischemic heart disease is a weakening of the heart caused by reduced blood flow, according to the nonprofit health system Advocate Health Care. The disease can increase a person's risk of blood clots, heart valve disease, heart failure and abnormal heart rhythms, among other conditions.

Atherosclerosis occurs when a person's arteries harden due to a plaque buildup, per Cleveland Clinic. The condition can "limit or block blood flow to various parts of your body, including your heart and brain," and possible complications include coronary artery disease, heart failure, heart attack, chronic kidney disease and stroke.

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'Unthinkable':Sam Rubin, longtime KTLA news anchor who interviewed the stars, dies at 64

Rubin, who joined the KTLA newsroom in 1991, was a fixture at red-carpet events and Hollywood awards shows, often speaking with A-list stars about their latest projects.

KTLA mourns the death of anchor Sam Rubin

Rubin died May 10 at the age of 64. As KTLA opened its 1 p.m. newscast, a group of the newsroom's anchors announced their colleague had passed away.

"The station is filled with great sadness," anchor Frank Buckley said at the time. "(Rubin) was here yesterday with us and called in sick. We learned the news this afternoon."

"We don't know what exactly happened, but we know it was sudden because he was here yesterday. Just over 24 hours ago we were sitting with him on this set," Buckley added.

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The news station paid further tribute to Rubin in a touching social media statement.

"KTLA 5 is profoundly saddened to report the death of Sam Rubin,” the statement read. “Sam was a giant in the local news industry and the entertainment world and a fixture of Los Angeles morning television for decades."

"His laugh, charm and caring personality touched all who knew him,” the statement continued. “Sam was a loving husband and father: the roles he cherished the most. Our thoughts are with Sam’s family during this difficult time."