A car bomb exploded outside an apartment building owned by alleged Colombian cocaine czar Pablo Escobar, killing two security guards and wounding five others. The explosion left a crater 12 feet deep and 21 feet across outside the eight-story Monaco apartment building in an exclusive suburb of Medellin. Two right-wing groups claimed responsibility for the attack, saying their intent is to rid the city of criminals and drug traffickers. But some residents linked the bombing to a massacre of 10 people last weekend in a Medellin mansion in what police said was a gangland revenge attack. Escobar heads the Medellin cartel, which officials say is responsible for 80% of the cocaine shipped to the United States.