Police are investigating the death of a man found on a Castro District sidewalk Monday afternoon with a knife sticking out of his chest.

Officers responded to the stabbing at 18th and Diamond streets just before 3 p.m.

The man was pronounced dead at the scene, San Francisco police spokesperson Officer Giselle Talkoff said.

It wasn’t immediately known whether the death was a homicide or suicide, according to Talkoff.

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