The park was partially closed for the investigation but has since reopened.
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Runners, walkers and their dogs trying to get to Bernal Heights Park Thursday morning were stopped by crime scene tape.
"To have something like this is really unusual because it is such a nice place," a jogger told ABC7 News.
Instead of exercising neighbors stopped to tell each other the news, that a jogger discovered a body on the trail at 5:30 a.m. Thursday. Police say he had been stabbed to death.
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"Wow I usually run up here early in the morning 6:00 a.m. glad I wasn't here this morning," said Lara Levin, a San Francisco resident.
Police spent the morning looking for clues -marking evidence as they found it. Some who use this park found themselves speculating about what could have happened in this usually peaceful place.
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"We also have a lot of night activity up here, a lot of kids who come to play or other things. We have a lot of homeless people who wander around so, who knows," said Julie Kendall, a San Francisco resident.
Some are now questioning if they are safe here. "I will be thinking twice about running here early in the morning by myself," one jogger told ABC7 News.
Anyone with information about this is asked to call the San Francisco Police Department's anonymous tip line at (415) 575-4444 or send a text to TIP411 and begin the message with SFPD.