  If two particles move toward a black hole and collide near the horizon, the
energy E_{c.m.} in the centre of mass can grow unbounded. This is a so-called
Ba\~nados-Silk-West (BSW) effect. One of problems creating obstacles to the
possibility of its observation consists in that individual energy E of a
fragment at infinity remains finite because of redshift. We show that in the
case of head-on collision, debris may have unbounded energy E. An essential
ingredient of this scenario is a particle moving away from a black hole in the
near-horizon region. It can appear due to precedent collision that implies
multiple scattering.
