The screams from thousands could be heard echoing down Polk Street from the filming of the movie "Milk," starring Sean Penn as Harvey Milk, the proclaimed "mayor of the Castro," at United Nations Plaza, on Sunday, March 9.

The streets in front of City Hall were jam-packed with howling extras dressed in 1970s ensembles, who unfolded the original gay pride flag, during the recreation of the 1978 Gay Freedom Day.

Penn was truly in character as he swung his fitful fists in the warm air, and in an New York accent, spoke intensely to his audience about gay pride just moments before they burst out into a melodic cheer of love.

"Harvey was revolutionary," said James Poole, 42, an extra for the movie and a gay rights activist. "And you could tell how much people really loved him, even in the reenactment for the filming."

"Milk" is based on the true story of the assassination of the first openly gay elected supervisor, Harvey Milk, and San Francisco Mayor George Moscone, who were both shot and killed by past San Francisco supervisor Dan White on Nov. 27, 1978.

During the day, a maroon and red striped 1970s MUNI bus sat parked on the corner at City Hall, while people stood on the roof of the ancient bus bearing the pride flag. Several old beige and blue colored Fords and Chevys took up the slots where Mayor Gavin Newsom's town car is usually parked.

Michael Boyle, 56, a retired history professor who studied and lectured at UC Berkeley, said that the filming of "Milk" is essential to teach the younger generation about San Francisco's history.

"Harvey Milk was a legend in San Francisco and a martyr in the gay community," Boyle said. "Milk helped shape San Francisco into the progressive city it has become and his name and his legacy should never be forgotten."

Vincent Heitkam, 46, who participated as an unpaid volunteer in the film project remembers the times surrounding Milk and his assassination well.

"I remember the unjustified verdict of Dan White like it was yesterday," Heitkam said.

White received less than eight years in prison for the murders, a verdict that sparked the "White Night" riots in the city, leading over 1,000 people to storm from the Castro to City Hall.

"I loved Harvey Milk. He represented my community and that is why I am here spending my Sunday in the hot sun with a couple thousand people," Heitkam said. "This is a cause worth participating in."

Filming of "Milk" will continue in San Francisco until the production wraps later this year