By Al Novack, Steve Beck

PHILADELPHIA (CBS) – One person was killed and three others, including a pregnant woman, were injured in a shooting in South Philadelphia Tuesday evening.

The deadly shooting happened at about 9 p.m. in the 1400 block of S. Etting Street in the Grays Ferry section.

According to investigators, a gunman, who was on a motorcycle, opened fire and struck four people.

Authorities say a 24-year-old man died after being shot in the back.

Among the three victims in stable condition is a 29-year-old pregnant woman who suffered a non-life threatening leg wound.

Investigators say they are searching for a black male with dreadlocks who fled the scene along N. 27th Street on a blue and black motorcycle.

A motive was not immediately known and the deadly shooting remains under investigation.