We report a theoretical investigation of the collision induced dissociation of pyrene dimer cation, as recently investigated in the experimental work by Zamith et al. (J. Chem. Phys. 153, 054311 (2020)). Molecular dynamics simulations using potential energies and forces computed at the self-consistent charge density functional based tight binding level were conducted for different collision energies between 2.5 and 30 eV. It appears that most of the dissociation occurs on a short timescale (less than 3 ps). The dynamical simulations allow to visualise the dissociation processes. At low collision energies, the dissociation cross section increases with collision energies whereas it remains almost constant for collision energies greater than 10-15 eV. The analysis of the kinetic energy partition is used to get insights into the collision/dissociation processes at the atomic scale. The simulated time of flight mass spectra of parent and dissociation products are obtained from the combination of molecular dynamics simulations and phase space theory to address the short and long timescales dissociation, respectively. The agreement between the simulated and measured mass spectra suggests that the main processes are captured by this approach.