Javier Lariano Gaitan (alias The Prince of Darkness) is a ruthless Colombian cartel member who was deemed responsible for the murders of 50 to 60 people during his course as a hitman. When Manuel and Natalie Ortega killed one of the cartel's dealers, Felix Arias, because Arias sexually harassed Natalie, Manuel retorted by killing them out of retribution. Gaitan was sent to murder the couple in a crowded restaurant out of revenge.
Finding out the gun Gaitin used, a Steyr Aug heavy duty rifle, Cerreta tried to arrest the dealer, George Lobrano, in a sting so he'd be a witness. That went out the window when Lobrano shot and nearly killed Cerreta, so Gaitan's girlfriend who was hiding him, Sandra Alvaro, gives her testimony. She does so from prison because her life was threatened, and she needed to protect herself. It was plenty for Gaitan's conviction of the two murders.
Gaitan was shot dead by Mr. Cristobal, who alleged his son was killed by Gaitan and he was seeking revenge. In reality, after pleading to manslaughter and being released on bail before allocution, it was revealed Cristobal was another cartel killer, sent to execute Gaitan so he wouldn't sell the syndicate out to the feds. Lobrano gave up Cristobal's act, but since he fled to Columbia 40 minutes after his release, with his wife draining his accounts, it was too late. All the witnesses who were in the vicinity of the case were murdered, to keep them from the justice system and assert the cartel's force. (L&O: "Prince of Darkness")