We present preliminary results of a numerical solution (by the Monte Carlo method) of the nonstationary radiation transfer equation for the case of an optically dense disperse medium. As a model medium, we took a homogeneous water droplet cloud. It is expected that an ultra short (about 50-fs duration) intense laser pulse stimulates nonstationary transient process inside the volume of a scattering particle. The result can be transformation in time of its optical characteristics and, primarily, of its scattering phase function. To calculate the dynamics of the scattering phase function of a transparent spherical particle, the nonstationary Mie theory was used, based on the Fourier transform of the initial light pulse and the linear theory of radiation diffraction on a sphere. The field scattered by a particle and the internal field inside the particle are written in the form of the integral of convolution of the pulse spectrum with the spectral response of the particle. Based on spatiotemporal diagrams of light intensity, we have isolated four stages in the nonstationary light scattering by a particle. Then the calculated optical characteristics of a particle have been used as input parameters in solving the problem on multiple scattering of the light pulse by a water aerosol.