The deadliest terror attack in SF history happened 100 years ago today The bombing of Market Street is almost unknown today but led to one of America's darkest miscarriages of justice.

The Preparedness Day parade moments before the deadly bombing. The Preparedness Day parade moments before the deadly bombing. Image 1 of / 18 Caption Close The deadliest terror attack in SF history happened 100 years ago today 1 / 18 Back to Gallery

July 22, 1916 was hot.

As members of the Grand Army of the Republic assembled at the Ferry Building, awaiting the start of San Francisco's lavish Preparedness Day parade, one elderly veteran fainted. Just as an ambulance reached the fallen man, a explosion shook Market Street.

When the dust settled, a bloody scene painted the street. The sidewalks ran red and "all around the bodies of men and women, almost stripped of their clothes, lay in horrible grotesque heaps," wrote the Chronicle. Windows blocks away were shattered. Ten were dead, including one child, and another 40 injured.

It remains the only terrorist attack in San Francisco history.

The day began as a great celebration, but it was not without controversy. The parade, the biggest in city history at over 51,000 marchers, was meant to celebrate the city's preparedness for World War I. The city was already at war with itself, however. Labor unions were locked in an all-out fight with business owners. Anarchists and anti-war demonstrators joined the voices against World War I and the nationalistic Preparedness Day parade.

Days before the parade, hundreds of businesses and individuals received a strange postcard in the mail. It was written in pencil with many of the words underscored boldly.

"Our protests have been in vain in regards to this preparedness propaganda, so we are going to use a little direct action on the 22d, which will echo around the earth and show that Frisco really knows how and that militarism cannot be forced on us and our children without a violent protest," it read.

"Things are going to happen to show that we will go to any extreme, the same as the controlling class, to preserve what little democracy we still have. Don't take this as a joke, or you will be rudely awakened."

The postcards were ignored.

Despite the shocking blast, the parade went on as scheduled. Bodies were still on the street when the parade continued on over the broken, bloody ground. Among the rubble, police found the bomb on Steuart and Market: a suitcase packed with bullets and shrapnel and set off with a timed explosion. Without a scrap of evidence, they knew who to blame.

"A man who would commit so dastardly and cowardly an outrage must be a man with anarchistic principles," San Francisco police chief D.A. White said.

When district attorney Charles Flickert arrived at the scene, he told reporters, "You know, men, I already think I know who did this."

Five days later, police arrested Warren K. Billings, 22, and Thomas J. Mooney, 33, without warrants. Billings, a shoe cutter from New York, was already well-known to police. He'd been arrested for the assault of the foreman at a shoe company in 1913 and had recently been found carrying explosives on a street car in Sacramento. But he was just the lackey, prosecutors argued. Mooney was the true mastermind.

Mooney had been on the police radar for years despite having no criminal record. He was one of the city's foremost radical leaders, a well-known socialist in the labor community. With the country roiling in anti-socialist sentiment, it's perhaps no surprise Billings and Mooney were singled out.

And the willing public had no qualms playing along, despite a complete lack of evidence. On July 27, Miss Estelle Smith was brought down to the City Prison to identify Billings as the bomber.

"You had better be careful, lady, I am not the man you saw," Billings said.

"I am careful," Miss Smith replied. "And you certainly are the man."

Another witness said the man who put the suitcase on Steuart Street "had on a dark suit and a broad-brimmed sombrero. There is little doubt he was a Mexican." A waiter near the blast couldn't keep his story straight, but he was sure he saw Billings and Mooney that day. One woman claimed to see them both instantaneously in different places on Market, a feat she accomplished with her "astral self."

But the most credible witness was the "honest cattleman" Frank Oxman. The rancher swore under oath he had seen the pair plant the suitcase bomb. But he wasn't in San Francisco at all that day; he was in Woodland buying cattle.

On Oct. 7, 1916, Billings was sentenced to life in prison. On Feb. 9, 1917, less than an hour after returning from dinner at the Washington Hotel, the jury came back with a guilty verdict for Mooney too. He was sentenced to death by hanging.

"The verdict does not make me guilty," Mooney declared as he was led away. "I am not guilty."

In the years that followed, it became clear that Billings and Mooney were hurriedly blamed to give DA Flickert a big political victory over labor activists. The waiter recanted his testimony. The honest cattleman's lie was revealed (and he was tried for perjury).

Meanwhile, a federal government investigation into the district attorney found even more damning evidence. They bugged Flickert's office and caught him admitting to orchestrating the frame-job of Mooney and Billings.

In light of the overwhelming evidence, Mooney's death sentence was reduced to life in prison by President Woodrow Wilson.

But still, the years went by. Finally, 22 years after being imprisoned, California Governor Culbert Olson signed a "full and unconditional" pardon for Mooney, then-called the most famous prisoner in the world. Billings, who had a prior felony conviction, would need a court recommendation to receive his freedom.

That night, Gov. Olson received a call from a superior court judge who admitted that he knew private detectives and San Francisco police had trailed Billings "every minute" the day of the parade. He could not have been the bomber.

Billings was officially pardoned and freed on Oct. 17, 1939.

The day Mooney was freed, he addressed 1,000 witnesses in the State Assembly chambers and, at times wracked by sobs, gave a speech that was broadcast around the country.

"I am not unmindful of the tremendous significance of this occasion," he said. "... We must establish real social order wherein the people will benefit one another and not profit at the expense of one another."

Mooney went on the speaking circuit for some time, but his health was irrevocably broken by years in prison. He died three years later; his funeral was held at the San Francisco Civic Auditorium (today's Bill Graham Auditorium).

Billings lived in relative anonymity until 1972, when he died after decades of quiet life as a watchmaker in San Francisco.

The real Preparedness Day bomber has never been found.