No laughter was ever loud enough for Robin Williams, a speed-of-instinct comedian whose most unpredictable act was his last.The Academy Award-winning actor and comedy legend was found dead Monday at his Tiburon, Calif., home, apparently of suicide by asphyxiation. He was 63.An investigation by the Marin County Sheriff's Office is continuing, including an autopsy planned for today."This morning, I lost my husband and my best friend, while the world lost one of its most beloved artists and beautiful human beings. I am utterly heartbroken," said Mr. Williams' wife, Susan Schneider. "On behalf of Robin's family, we are asking for privacy during our time of profound grief. As he is remembered, it is our hope the focus will not be on Robin's death, but on the countless moments of joy and laughter he gave to millions." It was an abrupt, stunning end to an extraordinary career, initially built upon quicksilver gags, freely associated and insanely performed. Like his idol Jonathan Winters, Mr. Williams' routines might be mistaken for lunatic ramblings except for their symmetry. Audiences couldn't tell where the jokes were going but assured themselves of a fun trip.In contrast to his manic sense of humor in public, Mr. Williams reportedly suffered from severe depression, the "tears of a clown" syndrome seldom taken seriously enough.Mr. Williams entered a rehab facility in July, soon after the cancellation of his CBS sitcom The Crazy Ones. His representatives denied that Mr. Williams had relapsed into addiction first addressed in the 1980s, after the overdose death of his friend and former Saturday Night Live star John Belushi. In addition, Mr. Williams underwent open heart surgery in 2009.Despite the failure of his television comeback — 35 years after exploding into pop culture as a wacky alien on Mork & Mindy — Mr. Williams' career appeared to be stable. A sequel to his Oscar-nominated role as Mrs. Doubtfire was in the works, and another turn as Teddy Roosevelt in Night at the Museum: Secret of the Tomb is due in December. Last year, Mr. Williams appeared as President Dwight D. Eisenhower in Lee Daniels' The Butler.Acting lent a measure of validity to Mr. Williams' early career, when it appeared that comedy improvisation might be the extent of his genius. His 1980 debut, in the seemingly tailor-made role of Popeye, was roundly panned. Mr. Williams stubbornly concentrated on serious roles until 1987's Good Morning Vietnam offered the right blend of pathos and prankster, earning his first of four Oscar nominations as an actor.A few years later, Mr. Williams won Best Supporting Actor for his role as a sympathetic psychologist in Gus Van Sant's Good Will Hunting. Most of his best performances — One Hour Photo and Insomnia come to mind — were in the same vein, drastic contrasts to his stand-up comedy persona, as if straining to prove the expanse of his talent, overcompensating for being so naturally hilarious.But it was onstage where Mr. Williams was an indomitable force of nature, impossible to interrupt so other comedians could only wait for him to wind down. His tireless efforts co-founding the Comic Relief charity program for homeless people was matched only by his performances at the show.Mr. Williams final stand-up comedy tour, the now-eerily titled Weapons of Self-Destruction, ended his six-year hiatus from the stage in 2008. In 2013, he made his final Tampa Bay appearance at Ruth Eckerd Hall in Clearwater, casually kibbitzing with fellow comedian David Steinberg.Comedy in the hands of Robin Williams was a whirlwind that is now sadly, suddenly stilled. So many laughs from perhaps the least quoted comedy genius ever, simply because the jokes flew too fast and furiously for memorization.The adage for comedians wishing to be taken seriously as actors is that comedy is easy and dying is hard. Here was a performer who made both comedy and acting look easy. It's the dying part about Robin Williams that each of us today is taking so hard.Contact Steve Persall at [email protected] or (727) 893-8365. Follow @StevePersall. Information from the Associated Press was used in this report.