We analyze the transient behavior of a pulse scattered by a double quantum dot Aharonov-Bohm interferometer. Our study uses the analytical solution of the time-dependent Schrodinger equation for cutoff Gaussian wavepackets incoming at the system. We find that the wavepacket evolution is governed by a dynamical Fano profile, which is a transient structure that travels embedded in the scattered wavepacket, whose shape and time evolution can be controlled by manipulations of the Aharonov-Bohm phase of the device. We demonstrate analytically that this transient structure is characterized by the energy and width associated to the Fano resonance. At long times and distances from the interaction region, the transient oscillatory structures fades away and both the Breit-Wigner resonance and Fano line-shape are fully imprinted on the Gaussian pulse. (c) 2012 Elsevier B.V. All rights reserved.