Disturbing video obtained by NBC Bay Area appears to show — in (be warned) shocking detail — one of several incidents of abuse that may have eventually killed 66-year-old homeless transient Stephen Williams, a man who reportedly lived within Golden Gate Park for some years.

On the morning of May 24, Williams was found dead in a small body of water, Alvord Lake. According to previous reports, two men in particular attacked Williams three times over the course of as many days, an act some familiar with situation are calling an instance "street justice." Williams had allegedly been caught masturbating near children in the park, an accusation against him that is audible in the video below.

Williams' two main attackers are allegedly 20-year-old Stephen Billingsley, who goes by "Pizza Steve," and 37-year-old Nikki Williams, who goes by the more ominous nickname "Evil." NBC reports that Billingsley pleaded not guilty to murder, torture, conspiracy, elder abuse, and assault on Monday in San Francisco Superior Court. Meanwhile, though Williams ("Evil," not the deceased), allegedly joined in on the attacks —perhaps with others according to NBC in a group known as "The Travelers" — he has not been charged with murder. Both men are being held on $1 million bail.

Williams (the deceased) reportedly has a history of mental health issues and homelessness in San Francisco but seemingly no criminal history of sexual offenses. The attacks on him began on May 22 — this video appears to show the first or second instance — and escalated in their nature, ending with Williams rendered unconscious and perhaps drowning as a result after he was allegedly dragged into the Alvord lake.

Previously: [Update] Homeless Man Found Dead In Golden Gate Park Allegedly Tortured For Three Days