A method of providing an indication of the direction of a target such as a sniper. A rifle mounted sensor array detects an acoustic pulse originating from the target. The signal is processed to estimate the direction of the target, and an indication is provided when the weapon is aligned with the estimated direction. The direction of arrival of an acoustic pulse is estimated by spectrally decomposing each signal from the sensor so as to generate one or more spectral components for each signal, and processing the spectral components to estimate the direction of arrival.