  Let G be a closed subgroup of the isometry group of a proper CAT(0)-space X.
We show that if G is non-elementary and contains a rank-one element then its
second bounded cohomology group with coefficients in the regular representation
is non-trivial. As a consequence, up to passing to an open subgroup of finite
index, either G is a compact extension of a totally disconnected group or G is
a compact extension of a simple Lie group of rank one.
