An argument turned violent in Ocean Beach when four people were stabbed early Wednesday.
The stabbing happened at Brighton and Bacon just after midnight, leaving a trail of blood on the sidewalk.
Two women and a man got into some sort of argument with two men walking toward them, San Diego Police said.
Someone took out a knife, stabbing two of the men and both of those women, officers said.
Police said they believe it was the man walking with two women who used the knife in self defense.
One victim was rushed to the hospital where he underwent surgery. Police said two of the victims were intoxicated and unable to provide information on the suspect.
Police described the injuries as non-life threatening. No arrests have been made.