Spontaneous acts of tribute sprang up at landmarks from his career.

In Boston, scores of people jotted tributes in chalk to Williams near a bench in the lush Public Garden downtown, which was featured in "Good Will Hunting."

Mourners hung signs, including "You will be missed" and "RIP Robin" on the wooden fence of the home in Boulder, Colorado, where parts of the intro credits for his breakout 1970s TV comedy, "Mork & Mindy," were filmed.

On the Hollywood Walk of Fame, fans congregated around Williams' star, leaving flowers and candles to honor the actor.

Interest in his film work spiked on Tuesday, with "Dead Poets Society" as well as "Mrs. Doubtfire" and "Good Morning, Vietnam" making it into the Top 20 in the iTunes movie chart.