Generally they're beaten up to death, but the "thrown off a bridge" bit seems routine to me. I may be completely wrong, but there seems to be, in my dysfunctional memory, the recollection of such an event every year or so in the press (not counting that there may be more that go unnoticed).

The most famous of course being Brahim Bouarram, in 1995, who was thrown into the Seine river by a group of skinheads who had just left a Front National meeting (Le Pen's party). An ex-homeless (or still homeless according to Libération at the time) Moroccan.