San Francisco police released a dramatic video showing an attacker fatally stabbing a British tourist in a bustling section of the city.The incident occurred Feb. 18 on Post Street near San Francisco's Civic Center. The video shows a robber chasing and then attacking the 44-year-old tourist in the middle of the street.The tourist died Thursday, officials said.Authorities said police were looking for two suspects and asked anyone who was in the area of Post between Franklin and Gough streets to contact police.Police told the San Francisco Chronicle that the victim was stabbed in the head after a man and woman tried to steal his messenger bag. The police said he tried to hold onto the bag, prompting the man to stab him. The Chronicle said the man was walking near his niece's home.