Test results on the gun that killed a prosecutor investigating Argentina’s worst terrorist attack have reignited the debate over how he died.

Results released late Monday show the gun that killed Alberto Nisman would have left traces of metals from the gun’s cartridges on the hand that pulled the trigger. Two tests done on Nisman’s hands a few days after his death showed no traces. His ex-wife, Judge Sandra Arroyo, says the new test on the gun proves someone else shot him.

“Ballistic experts told me that in 100% of the cases that this .22-caliber Bersa pistol was fired with the same kind of ammo (that pierced Nisman’s skull) it would leave traces on the person firing the shot,” Arroyo told local Radio Mitre.

Nisman led the investigation into the unsolved 1994 attack on a Jewish center that killed 85 people. He was found 18 January in his apartment with a bullet in his head. He had been scheduled the following day to elaborate to congress on his allegations that President Cristina Fernandez had orchestrated a secret deal to cover up the alleged role of Iranian officials in the bombing.

Fernandez rejected the allegations and local judges threw out the case.

Lead prosecutor Viviana Fein says the latest test is inconclusive and doesn’t determine if he killed himself or was slain by someone else. Fein also challenged Nisman’s ex-wife to come up with “direct and concrete” proof that the late prosecutor was killed.

Local media reported that the tests were carried out at a laboratory in the northern Argentine city of Salta. Investigators reportedly tried to recreate the shooting by using pig skin to cover up the hand of a mannequin and then firing a shot using the pistol that killed Nisman.

The test results were first released to local press. Fein said they cannot be fully accurate because they cannot recreate the crime scene. “We can’t take one piece of proof in an isolated way,” she said. The prosecutor has said the investigation will continue and is expected to conclude in October.