Mexican authorities say a man has opened fire at a prosecutor's office in the western state of Jalisco, killing a woman and wounding three more. The assailant was also shot dead, by security guards.

Jalisco state Attorney General Eduardo Almaguer says the shooter was armed with two pistols during Wednesday's shooting. Three of the four victims including the woman who died were social workers, and the motive was not immediately known.

Almaguer said the 56-year-old shooter had worked around the prosecutor's office doing administrative paperwork and was well-known by most in the building.

He faulted security at the entrance for allowing the man to enter with weapons.