A shocking broad-daylight stabbing outside a Burger King in South of Market on Tuesday killed a 42-year-old San Francisco man, police said.

Kenneth Lyon was sitting on the curb outside the fast-food joint at Ninth and Natoma streets when the attacker walked up behind him and stabbed him once in the middle of his back about 6:40 p.m., police Sgt. Michael Andraychak said.

Lyon succumbed to his wounds at San Francisco General Hospital, Andraychak said.

A witness to the cowardly attack flagged down nearby police officers, who made a swift arrest, Andraychak said.
Clenny Thierry, 52, was arrested on Howard Street, just east of Ninth Street. He was booked into County Jail on murder charges, Andraychak said.

The killing marked the 22nd homicide in San Francisco this year.