Another suspect has been arrested in the May torture and killing of 66-year-old Stephen Williams near Alvord Lake in Golden Gate Park, according to the Examiner. 

27-year-old Michael Grasso was arrested on Tuesday and booked on suspicion of murder and inflicting injury on an elder. It's not clear how he was involved in the case, in which Williams was allegedly beaten for days before he was killed. It's speculated that the killings were a form of "street justice" after Williams, who was homeless, allegedly exposed himself to and masturbated near children in the park. 

Two other suspects, 20-year-old Stephen "Pizza Steve" Billingsley and 37-year-old Nikki Lee "Evil" Williams, were arrested on May 24th, the same day Williams' body was found in Alvord Lake. They've pleaded not guilty to all charges. A third suspect, 23-year-old Ian Severa, has also been charged with murder. 

Update, 5:19pm: According to the Chronicle, a second suspect was also arrested on Tuesday: 19-year-old Sahmanntha Rundstrom, who was found after posting on social media that her car had broken down near Flagstaff, Arizona and she needed a ride. Noted as a "homeless panhandler and camper" by Flagstaff police, she's set to be extradited to San Francisco. It's not clear what she'll be charged with at the moment.

Grasso, who was arrested near Golden Gate Park, is being held on $1 million bail.