The San Francisco park where three people were shot on a sunny afternoon underwent a $20 million renovation last year and immediately became one of the city's most popular destinations — and a magnet for drug use, gang activity and violence.

The new playground, additional bathrooms and improved amenities of the park in a gentrifying neighborhood of trendy restaurants and bakeries attracts dog walkers, families and young tech workers. Facebook founder Mark Zuckerberg's $10 million home overlooks the park.

But the 13-acre (52,600 square-meter) park with spectacular skyline views and a high school across the street sits in the middle of the Mission District neighborhood, which is still dominated by gangs and homeless drug users.

The shooting Thursday afternoon at the park that sent families and other visitors scurrying for cover appeared to be a targeted incident, and investigators are looking into gang ties, San Francisco police spokesman Robert Rueca said. The assailants wore red shirts and bandanas covering their faces, witnesses said.

Supervisor Jeff Sheehy, whose district includes the park, called for a "top-to-bottom" review of security for the park and said a stepped-up police presence if necessary. "We have to do everything we can to make the park safer," he said.

Police said Friday they are increasing patrols of uniformed officers in the park.

Thursday's shooting occurred on a bridge that connects the park to the neighborhood and spans a train track. Police and others said the bridge is a source of many of the park's problems because drug use can be easily hidden and it offers easy escape.

A Feb. 9 police report showed two men told officers they were smoking methamphetamine under the bridge when two men walked up to them and asked "where you from" before one of the men shot one of the smokers in the arm.

Police said they could not immediately provide the number of times officers have been called to the park this year and last.

The park has been the location of several recent high-profile incidents, including a group of young attackers beating, stabbing and seriously wounding a 23-year-old man on the afternoon of May 17. Fights erupted in the park the night after the city's annual Gay Pride parade June 25. A woman was hit in the head with a bottle and a man was stabbed.

On July 10, a 20 -year-old man was stabbed during an afternoon brawl involving about a dozen youths, police reported. Skateboarders and police clashed violently last month after officers tried to break up an unsanctioned skating contest at the park.

"Everybody in the community is concerned," said Peter Lewis, a neighborhood activist. "It's getting worse."

Frank Diaz was tying helium balloons to picnic tables and laying out food for a company picnic Friday near the bridge where the shooting happened.

"Of course, I panicked," Diaz said about hearing about the shooting. "I have been planning this for months."

Diaz, 43, said he went ahead with the picnic after police assured him uniformed officers would patrol the park.

On Friday, underneath the bridge, Ryan Murphy and Rose Sergeant walked the train tracks with trash pickers, picking up discarded syringes and needles. The two spend about 10 volunteer hours a week picking up and disposing of used needles throughout the city. They said they found eight Friday morning.

"This is a place where we come often," Sergeant said.

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This story corrects the spelling of Frank Diaz's first name.