SAN FRANCISCO — San Francisco has embraced the bicycle.

In the past five years, the number of bikes in the city jumped 71 percent and it now ranks fourth — behind Portland, Minneapolis and Seattle — in how many people bike to work, according to the U.S. Census Bureau.

But a recent bicycle-related death has set the cycle-loving city on edge. On Thursday, George Gascon, the San Francisco district attorney, said he would charge a bicyclist with felony vehicular manslaughter for reckless riding that resulted in the death of a pedestrian.

On March 29, Chris Bucchere, 36, a software developer, was riding his bike down a hill in the Castro District. Police officials say footage from a store's surveillance camera put his speed as fast as 35 mph.

Bucchere — while crossing a busy intersection when a traffic light turned red — struck Sutchi Hui, 71, as he and his wife crossed the street. Hui died several days later.

News of the crash spread rapidly after people began sharing an online post on a cycling website that police officials believe Bucchere wrote. In the post, the writer describes the moments before the collision, saying he was "too committed" to stop at the light.

"I laid it down and just plowed through the crowded crosswalk in the least-populated place I could find," the post read. The entry goes on to detail the "river of blood on the asphalt" coming from Hui.

Though no agency tracks national data on the severity of charges in such cases, many cycling advocates and law-enforcement officials said this was the first felony charge they had heard of in such a case.

"I'm hoping this case serves to raise awareness for everyone that the rules of the road apply to everyone," said Gascon, who said Bucchere could be sentenced to as many as six years in jail.

Bucchere's lawyer said he had turned himself in and is cooperating with the investigation.

Some 4,834 cyclists and 59,925 pedestrians were killed by motor vehicles in the U.S. between 1999 and 2009 (the most recent year for which figures are available), according to the Centers for Disease Control and Prevention. Cyclists killed 63 pedestrians, or about six a year, during the same period.

The rarity of such cases is little comfort to residents in the Bay Area, where three people have been killed by cyclists in less than a year. The most recent victim was a 92-year-old woman killed June 6 in a crosswalk in nearby El Cerrito, Calif..

Cases like these tend to amplify existing ire between cyclists and other road and sidewalk users. "They think they own the streets," said Pascal Bouchet, 53, who has been driving a taxicab in the city for 29 years.

Bouchet said it is not just the oft-maligned bicycle messengers who are reckless, but the tourists who rent bikes to take in the sights. "They're in vacation mode, spacing out, bicycling like they're on the back roads in the south of France," he said.

Most cyclists follow the rules of the road, but some contend some riders knowingly flout the law. An editorial in the San Francisco Chronicle called these riders "aggro bikers."

Cycling advocates say such negative associations are based on outdated stereotypes. "We are seeing more and more people bicycling, and it's not just 22-year-old aggressive males like it was 15 years ago," said Leah Shahum, who leads the San Francisco Bicycle Coalition.

The number of trips made by bicycle in the U.S. more than doubled in the past decade, according to the U.S. Transportation Department and Federal Highway Administration. Meanwhile, cyclist deaths have fallen by 21 percent since 1988.

"What you see is that as the number of bicycles goes up, the number of crashes goes down," said Andy Clarke, president of the League of American Bicyclists.

Pedestrian advocates say more needs to be done to protect the most vulnerable: the bipeds without wheels.

Nancy Gruskin, 51, of Westfield, N.J., started a foundation to do that after her husband was killed by a food-delivery cyclist going the wrong way on a Manhattan street in 2009.

"What happened to my husband is rare," said Gruskin. "But if you're going to have more cyclists on the streets you need to do more to protect pedestrians."