The self-force and the self-energy (Coulomb-velocity energy) of an electron moving along a rectilinear trajectory in the vacuum is analyzed numerically. It is illustrated for the first time that when the velocity of the electron approaches the light velocity in the vacuum, the Coulomb-velocity energy approaches infinitely large, so is the self-force that calculated with the Lorentz force formula. Consequently, electrons cannot be accelerated to move faster than the light in the vacuum using electric accelerators because infinite large external force may be required to make the electron cross the electromagnetic barrier of the light velocity in the vacuum. Based on the observation, the Bertozzi experiment is re-interpreted, which shows that the velocity limit is due to the intrinsic behavior of the electron that can be clearly explained with the classical Maxwell’s theory. It is obviously not so definite that this behavior of the electron is due to the effect of special relativity as claimed in text books. Therefore, the outcome of the Bertozzi experiment may be not an unquestionable experimental support to the Einstein’s theory of special relativity. It is natural to consider that neutral particles may move faster than the light velocity in the vacuum because they do not face the infinite electromagnetic self-force when they cross the electromagnetic barrier. Furthermore, a reasonable hypothesis can be made that superluminal electrons may be generated by the collision of high energy neutral particles in a collider or in the universe.