The Globe and Mail

At a wildlife park near Johannesburg, a helicopter is used to dart the rhino and track it from the air until it collapses from the tranquilizer. Then veterinarians began a treatment on its horn in an attempt to deter poachers.

A veterinarian takes the sedated rhino's pulse from a vein on its ear. The rhino's ears are stuffed with cotton to muffle sounds, and a towel is wrapped around its eyes to help keep it calm.

Veterinarians begin the process of drilling into the rhino's horn. In the treatment process, a DNA sample is taken, and holes are drilled so that veterinarians can infuse the horn with indelible dye and an anti-parastic drug that is toxic to humans if consumed. A microchip and tracking device are also inserted.

Veterinarian Charles van Niekerk drills into the rhino's horn. In the treatment process, a DNA sample is taken, and holes are drilled so that veterinarians can infuse the horn with indelible dye and an anti-parastic drug that is toxic to humans if consumed. A microchip and tracking device are also inserted.

The rhino is rolled over by park rangers during the treatment procedure. The southern white rhinoceros can weigh up to 3,500 kg.

A veterinarian drills into the rhino's horn. In the treatment process, a DNA sample is taken, and holes are drilled so that veterinarians can infuse the horn with indelible dye and an anti-parastic drug that is toxic to humans if consumed. A microchip and tracking device are also inserted.

A veterinarian drills into the rhino's horn. In the treatment process, a DNA sample is taken, and holes are drilled so that veterinarians can infuse the horn with indelible dye and an anti-parastic drug that is toxic to humans if consumed. A microchip and tracking device are also inserted.

The rhino's horn is sealed with epoxy resin and wrapped in duct tape after the treatment is completed.

Throughout the horn treatment, the sedated rhino's feet made a twitching or "paddling" motion that vets said is common when animals are immobilized. But later the rhino began convulsing, its feet and body shaking. The rhino failed to wake up from sedation, and died shortly after the horn procedure was completed.

Veterinarians try to wake up the sedated rhino after the horn treatment is complete. But the rhino, named Spencer, failed to regain consciousness, and died. Vets suspect it had a chronic heart condition, and may have suffered a heart attack, but an autopsy will take place to determine the exact cause of death.