A man walking down a SoMa street was suddenly attacked Wednesday afternoon, and police say that his assailant remains at large.

According to the San Francsico Police Department, the 51-year-old male victim was walking on the 100 block of Howard Street, which is between Main and Spear Streets, at 1:14 p.m. Wednesday when the attack occurred.

Police say that am man in his 30s S approached the victim "and began yelling," even though the victim "had no idea what [the suspect] was yelling about."

The suspect then punched the victim. The victim, attempting to extricate himself from the situation, kept walking, but the suspect then approached him from behind and struck him yet again.

Eventually, onlookers separated the two men, and the suspect apparently fled.

The victim, who police say was left in "serious" condition, was transported to an area hospital for treatment of his injuries. The suspect remains at large, and no arrests have been made in this case.