- The attack occurs hours before a peace concert
- The slain prosecutors worked for an anti-extortion unit
- A 12-year-old is injured in the attack, witnesses say
- Police are searching the area for suspects
Gunmen ambushed and killed three state prosecutors in front of a school in the border city of Juarez on Wednesday, authorities said.
The slain prosecutors were investigators for the office's anti-extortion unit, said Arturo Sandoval, spokesman for the Chihuahua State Attorney General's Office.
A 12-year-old was injured in the attack, witnesses said.
Students at the school, about 50 meters from the shooting scene, screamed as the sound of guns filled the air, according to witnesses.
Police were searching the area for suspects Wednesday.
The attack came just days before federal police are expected to pull back forces from the violence-plagued border city and hours before the popular band Mana was scheduled to perform a peace concert there.
Juarez is Mexico's most violent city and has become a symbol of the brutal realities of the nation's drug war, which has claimed more than 34,600 lives in less than five years.
Thousands of federal police have been patrolling Juarez since they officially took over its security operation from the Mexican military in April.
Earlier Wednesday, authorities in Chihuahua state's capital, also called Chihuahua, said six people were killed in a shootout inside a house.
Other Mexican states also saw violence Wednesday.
At the University of Advanced Studies in Saltillo, Cuahuila, professors made students huddle in an assembly hall as a series of shootouts shook the neighborhood.
"We were all scared, calling home. They had us there for an hour," student Ian Carlo Massu Davila said.