From what I remember from reading articles when this happened and also reading the fairly lenthy Wikipedia article, the agents appeared to be poorly trained for this type situation and that the bullets used were old fashion round nose bullets that didn't do as much damage as a modern bullet would do.

The article that I read stated "Toxicology tests showed that the abilities of Platt and Matix to fight through multiple traumatic gunshot wounds and continue to battle and attempt to escape were not achieved through any chemical means. Both of their bodies were drug-free at the time of their deaths."