Following the signing of Dingane and Retief's treaty, Piet Retief and his party were treated to a farewell dance by the Zulu impis at Ungungundlovu. They were told to leave their firearms outside the royal kraal. Suddenly, when the dancing had reached a frenzied climax, King Dingane leapt to his feet and shouted Bambani aba thakathi! (Catch the wizards!). The men were totally overpowered and dragged away to a hill called kwaMatiwane, named after a chief who had been killed there. Retief and his men were savagely butchered to death. It is alleged by some that the reason why they were killed, was because they withheld some of the cattle recovered from Chief Sekonyela. The general opinion is that Dingane did not wish to yield the land ceded to them in the treaty and mistrusted the presence of the Voortrekkers.

Sources:

Wallis, F. (2000). Nuusdagboek: feite en fratse oor 1000 jaar, Kaapstad: Human & Rousseau.

http://www.news24.com/News24/On_this_day/On_this_day/0,6119,2-1602-1492_1476405,00.html

http://www.andibradley.com/whatya/feb06.htm