• Mike Hagerty, known to many as Mr. Treeger from "Friends," died of a "sudden illness" on May 5
  • The 67-year-old actor suffered a seizure and entered a coma after he was given new antibiotics
  • Hagerty's cause of death was not determined to be COVID-19-related as he had tested negative for the disease

Mike Hagerty died earlier this month after his strong, adverse reaction to new medication caused him to go into a coma, according to a report.

The 67-year-old actor's energy was still low after he suffered a leg infection in April, unnamed sources close to Hagerty told TMZ.

Hagerty was set to begin filming the second season of the HBO comedy-drama "Somebody Somewhere," so a doctor sent him to the hospital for a checkup. While there, he was given a new antibiotic, according to the report.

However, he died at Cedars-Sinai Medical Center in Los Angeles on May 5 after he had an adverse reaction to the medication. He suffered a seizure and went into a coma, the report said.

His cause of death was described by the Chicago Sun-Times as a "sudden illness." TMZ said it was not COVID-19-related as the actor had tested negative for the disease.

Hagerty is survived by his wife Mary Kathryn and his sister Mary Ann Hagerty, according to his "Somebody Somewhere" co-star Bridget Everett.

Everett announced the news of his death via an Instagram post Friday, saying her late co-star "will be sorely missed."

"A beloved character actor, his love of his hometown of Chicago and his family were the cornerstones of his life," she wrote.

Fans also paid tribute to Hagerty online after hearing of his death.

"Funny, sweet and a total pro. Thanks for the decades of laughs," one person wrote on Twitter.

"Mike Hagerty was a great actor and a great man. I'm going to miss him. He lives forever in our hearts," another said.

HBO, for its part, released a statement following Hagerty's death.

"We are very saddened to hear about the sudden passing of Mike Hagerty. A member of the HBO family for many years, his most recent role as Bridget Everett’s father in 'Somebody Somewhere' showed his special talent for bringing heart to a performance. Mike was a joy to work with and brought warmth and kindness to all who knew him. We send our deepest condolences to his family and friends," the company said.

Hagerty is known for his role in the sitcom "Friends" as Mr. Treeger, the building superintendent of the show's main characters.

He also appeared in other television series over the course of his career, including guest spots on "Boston Legal," "Brooklyn Nine-Nine," "Cheers," “Community," "CSI," "Curb Your Enthusiasm," "Entourage," "Glee," "Grey’s Anatomy," "Happy Endings," "Shameless" and "Seinfeld," among many others.

IMDb credited Hagerty with a total of 115 roles.

Overall, the U.S. has reported a total of 82,376,975 COVID-19 cases and 997,215 virus-related deaths, according to data provided by the Centers for Disease Control and Prevention.

Mike Hagerty (L) and Mark Duplass
Mike Hagerty (L) and Mark Duplass attend HBO MAX "Somebody Somewhere" Finale Episode Screening at NeueHouse Los Angeles on February 23, 2022 in Hollywood, California. Charley Gallay/Getty Images for HBO Max