UMZIMKHULU, South Africa — Their fear faded as they raced back home, the bottle of Johnnie Walker getting lighter with each turn of the road. Soon, Sindiso Magaqa was clapping and bouncing behind the wheel of his beloved V8 Mercedes-Benz, pulling into familiar territory just before dark.

Minutes later, men closed in with assault rifles. Mr. Magaqa reached for the gun under his seat — too late. One of his passengers saw flashes of light, dozens of them, from the spray of bullets pockmarking the doors.

The ambush was exactly what Mr. Magaqa had feared. A few months before, a friend had been killed by gunmen in his front yard. Then, as another friend tried to open his front gate at night, a hit man crept out of the dark, shooting him dead. Next came Mr. Magaqa, 34. Struck half a dozen times, he hung on for weeks in a hospital before dying last year.

All of the assassination targets had one thing in common: They were members of the African National Congress who had spoken out against corruption in the party that defined their lives.