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Two men were shot to death as they sat in a Chevy Camaro in the playground parking lot.
"This is a very popular park, so there might've been some joggers or people who witnessed this," said San Francisco Police Department spokesman Officer Albie Esparza.
Police got the call at 9:36 a.m. from park workers and were on the scene two minutes later.
The male victims are in their 20s. The suspects are - for now - simply described as two males.
"We don't know the motive," said Esparza. "Preliminarily, there was some information that one suspect might've fled on foot, that another might've fled in a vehicle."
Broken glass, clothing and bright yellow markers surrounded the car Monday morning as investigators gathered evidence.
The killings are the city's twelfth and thirteenth homicides this year. Last year at this time, there were five homicides. Police say these deaths are part of a trend of multiple killings in San Francisco.
Distraught family members and friends rushed to the crime scene and spoke to officers as the car was towed to an impound yard. About two dozen mourners gathered later at San Francisco General Hospital. Police say they are trying to determine if the shootings were targeted and/or gang-related.
"Every shooting and stabbing in San Francisco, any violent crime, our Gang Task Force will always take a look at it to see if it is gang-related or not or if it's gang-motivated," said Esparza.