Enzo Markovic was a doctor associated with Project Helix. He was killed ironically by the man he doppelganged: James Lennox.
Enzo Markovic had his men capture CIA agent James Lennox and (while having the same face as him) took his place in an undercover mission. While sleeping with Emma Wallace, another CIA agent and Lennox's girlfriend, he knocked her out.
The next day, some of his men dumped her body on the street...wrapped in bubble wrap and C-4. Enzo made Emma sing "Pop Goes The Weasel" while he observed her from a phone booth. After singing for a few minutes, he detonated the C-4 and instantly incinerated Emma.
Enzo wasn't seen again until he found out that Sydney and Lennox were assaulting his frieghter compound, which contained key components of Project Helix. He managed to convince the CIA and Sydney that he was the real James Lennox and Sydney tied up Lennox, shortly before meeting up with Enzo. Enzo and Lennox cornered Sydney and, realizing there was no way to identify the real Enzo, activated the detonator in the Project Helix feighter. Enzo, wanting to change back to his normal body, pointed the gun at Sydney. The real Lennox shot Enzo twice and Sydney destroyed the freighter.