Two young brothers, their grandmother and a man were fatally struck by a car on a Southern California street, police said Wednesday.

The collision occurred after 8 p.m. Tuesday in the north San Diego County city of Escondido.

A 33-year-old man and and an 11-year-old boy died at the scene, an Escondido Police Department statement said.

A 50-year-old woman and her 10-year-old grandson died of their injuries at Palomar Medical Center.

Lt. Scott Walters said the 33-year-old man was part of the “family unit” but he did not know his relationship to the woman or her grandsons.

The driver of the 2014 Mazda 3 was taken to Scripps Memorial Hospital for treatment of moderate injuries, police said. She was only identified as a 28-year-old woman from Escondido.

Neither alcohol nor drugs appeared to be a factor but the crash remained under investigation, police said.

Escondido is about 30 miles (48 kilometers) north of downtown San Diego.