San Francisco's wave of knife crime struck again in the Tenderloin early Sunday morning. A 42-year-old victim was left in critical condition after a group of six men in their 20s approached him from behind and stabbed him in the back near Golden Gate Avenue and Hyde Street.

All six suspects fled the scene and had not been found as of Monday morning, according to police. The victim's stab wounds were considered life-threatening and he was taken to a nearby hospital.

As usual, anyone who might have any information about the attack is encouraged to contact SFPD's anonymous tipline at: (415) 575-4444 or via text message to TIP411.