Authorities say a 7-year-old boy, three women and a university professor are among 15 people who were killed in a single day in the Mexican border city of Ciudad Juarez.

State prosecutor's spokesman Arturo Sandoval says the child was traveling with his father in a pickup truck when gunmen opened fire Friday, killing them both.

Sandoval says three women were shot to death in two separate incidents. A university professor was killed in a residential area.

Sandoval says that nine other men were killed in six separate incidents.

The metropolis across the border from El Paso, Texas, is Mexico's deadliest city, with more than 1,700 killings so far this year.