With no death certificate available yet, investigation into Shandling's death remains ongoing, the Los Angeles County Department of Medical Examiner-Coroner tells PEOPLE

By Jodi Guglielmi Lanford Beard
March 25, 2016 12:00 PM

A day after his unexpected death, PEOPLE has learned that Garry Shandling collapsed as he called for help.

Assistant L.A. County Chief Coroner Ed Winter told PEOPLE that Shandling, 66, called 911 himself before collapsing and being taken to St. Johns in Santa Monica, California, where he died Thursday. (It’s been reported that the comedian suffered a heart attack at his home, though Winter said the investigation remains ongoing.)

Winter also revealed that Shandling does not yet have a death certificate: “There’s no doctor to sign the death certificate and we are looking into it. That’s all I can say at this time.”

Since Shandling’s death, tributes to The Larry Sanders Show and It’s Garry Shandling’s Show star have been pouring in from friends and fellow comedians.

“Sunday, my longtime friend Garry Shandling was here, making every1 laugh,” tweeted Kathy Griffin, who’d just spent time with Shandling and Better Call Saul star Bob Odenkirk this past weekend. She continued, “I loved him. I’ll miss our talks the most,” and Odenkirk added, “I can’t believe this. Very sad to say goodbye so abruptly.”

Conan O’Brien also dedicated his Conan monologue to Shandling on Thursday night, saying, “He was a masterful writer, a performer who went on to create incredibly groundbreaking comedy show that inspired an entire generation of comedians, myself included.”