A disturbing fatal stabbing Monday afternoon outside the post office on 18th Street in the Castro is now being treated by police as a suicide. As the Bay Area Reporter reports, the victim had a note beside him detailing next of kin, and discussing why he decided to end his life.

The victim, who died on the scene of a stab wound to the chest, has been identified as 63-year-old Peter Robinson, originally of Madison, Wisconsin. It is unclear if he was homeless at the time of his death, but he had a small shoulder bag with him containing a passport and some other items. Police say no drugs were found on his person, and a toxicology report has yet to confirm if he had drugs in his system.

Captain Daniel Perea of the Mission police station tells the BAR that "there were no reports of someone screaming or yelling for help," and Robinson was found with a fatal stab wound to the chest. Earlier reports from witnesses suggested the weapon was a kitchen knife.

Perea, not disclosing the contents of Robinson's note, says he does not know the reason for the suicide, and that Robinson was not a familiar figure on the streets of the neighborhood. "It's a sad incident, but it was one individual who was despondent acting on his own," Perea told the paper.

The BAR spoke with Andrea Aiello, executive director of the Castro/Upper Market Community Benefit District, who said that Perea had told her that Robinson had used the side of the post office building to press the knife in "deep." Perea would not confirm that account, however.

If you are in crisis, text "BAY" to 741741 for free, 24/7, confidential crisis support from Crisis Text Line. And if you or someone you know is having suicidal thoughts, you or they should call the San Francisco Suicide Prevention crisis line at (415) 781-0500.

If someone you know exhibits warning signs of suicide: do not leave the person alone; remove any firearms, alcohol, drugs or sharp objects that could be used in a suicide attempt; and call the U.S. National Suicide Prevention Lifeline at 800-273-TALK (8255) or take the person to an emergency room or seek help from a medical or mental health professional.