Ion-beam cancer therapy has become increasingly favored worldwide in treatment of certain types of cancerover the last decade. Whereas the clinical effects of the therapy are well documented, the understanding of the underlying physical mechanisms is somewhat incomplete. The problem arises due to the multiscale nature of the effects involved in ion-beam cancer therapy, as the effects range from quantum-mechanical to macroscopic scales. The present study investigates the production of free electrons in the vicinity of the Bragg peak through quantum-mechanical simulations of the collision between a C4+ ion with a cytosine-guanine nucleotide pair taken from a DNA double helix. Time-dependent density-functional theory was employed using the OCTOPUS 6.0 software. The results show that such a collision triggers the release of a large amount of electrons into the cellular environment, as only a fraction is captured by the C4+ ion. Furthermore, it is demonstrated that the impact angle and projectile kinetic energy have much more influence on the number of ejected electrons than the impact parameter.