Virginia ? An 18-year-old gunman opened fire outside a Chantilly police station Monday, killing one officer and wounding two others before he was shot and killed, authorities said. No motive was disclosed.

A 40-year-old female detective died at a hospital after the shooting, said police Chief David Rohrer, who did not identify the woman, a nine-year veteran of the Fairfax County Police Department. A second officer was in serious condition and undergoing surgery late Monday. A third was treated for minor injuries from flying glass or a ricocheting bullet.

Authorities did not identify the gunman. They were uncertain whether he shot himself or was killed in the exchange of gunfire.