It is probably more complex than simple thuggery, but *once again* a band of Chavista ruffians have launched tear gas canisters into places and residences of those seen as opposing the Chavez regime in Venezuela.
*Here* is the original report, in Spanish.
The gang, known as "La Piedrita", has been implicated in previous attacks, including those against private broadcaster Globovision and the residences of publishers of opposition periodicals.
The Vatican Nunciature has offered protective asylum to anti-regime student activist Nixon Moreno, but has not managed to get him out of the country yet. That might explain the targeting... or it might be because it's pretty obvious that the Catholic Bishops of Venezuela aren't exactly supporting Chavez.
Important Point, however: An Apostolic Nunciature is an EMBASSY. Failure to protect such is a severe violation of treaty.