An elderly woman suffered life-threatening injuries and three others were also hurt Sunday, when a man inexplicably pepper-sprayed a woman as she waited to board Muni.

According to the San Francisco Police Department, the incident occurred at 1:48 p.m. Sunday, on the 2300 block of Mission Street, which is between 19th and 20th Streets.

Police say that the five victims — an 86-year-old woman, a 56-year-old woman, a 66-year-old woman, and a 68-year-old man — "were in line for the bus."

Suddenly, the suspect pepper-sprayed the 66-year-old victim, police say. In the resulting panic, the 68-year-old man attempted to intervene, and was shoved by the suspect, and the 86-year-old woman fell into the street "causing injury." The 56-year-old was also injured in the scrum.

Police say that the woman who fell into the street suffered life-threatening injuries. She was rushed to an area hospital for treatment, according to the SFPD.

Additional details regarding the suspect or the motive in the pepper-spraying wasn't immediately released by police as of publication time. They do confirm, however, that the suspect in the case has been arrested.