A U.S. military investigating officer recommended Tuesday that a National Guard soldier be court-martialed for murder in the death of two of his superiors in Iraq in June.

Col. Patrick Reinert said he found "reasonable cause" to believe that Staff Sgt. Alberto B. Martinez, of Troy, New York, used an anti-personnel mine and three grenades to kill a captain and a lieutenant in a "personal vendetta."

The killing of Capt. Philip Esposito and Lt. Louis E. Allen in an explosion at a base near the central Iraqi city of Tikrit (search) is believed to be first case of an American soldier in Iraq accused of killing his superiors.

Reinert said he also found aggravating factors that could allow for capital punishment.

Reinert's recommendation, which came at the end of a two-day hearing in this camp in Kuwait, will be submitted to Lt. Gen. John Vines, the commander of Multi-National Corps Iraq (search), who will decide whether there is a court-martial. Vines, who is based in Baghdad, reports to the overall commander in Iraq, Gen. George Casey (search)

The prosecutor, Capt. Adam Siple, had asked for a recommendation for a court-martial. Martinez's defense counsel had argued there was no real evidence against their client.

Capt. Esposito, 30, of Suffern, New York, and Lt. Allen, 34, of Milford, Pa., were killed by a blast in Esposito's office in a former Saddam palace that is used as a base in Tikrit, some 80 miles north of Baghdad, on June 7. Their deaths were initially thought to be a result of "indirect fire" on the base — a mortar round that struck a window on the side of the building where Esposito and Allen were.

Senior Master Sgt. Kevin Fitzgerald, an expert on explosives, told the hearing that the blast was caused by a Claymore anti-personnel mine and possibly three grenades. Surgeon Col. Joan Sullivan told the tribunal that the men's injuries were not consistent with wounds caused by a mortar or rocket.

During Monday's session, one witness, Capt. Carl Prober, said Martinez told him twice that he hated Esposito — once in September 2004 and again in May. In the second instance, Martinez said "specifically I hate (Esposito) and I'm going to frag (him)," Prober testified. "Frag" is a Vietnam War (search) term for soldiers killing their superiors.

Prober did not say why Martinez said he hated Esposito.

The widows of Esposito and Allen attended the hearings after the Army agreed to fly them to Camp Arifjan, about 40 miles south of the capital of Kuwait City, for the sessions.

Martinez, 37, a supply specialist who joined the New York Army National Guard in December 1990, was deployed to Iraq sometime after October 2004 with the 42nd Infantry.

The Tikrit case is the second case during the Iraq war in which a U.S. soldier has been charged with killing his comrades.

In April, a sergeant in the Army's 101st Airborne Division (search), Hasan Akbar (search), was convicted of murder and attempted murder for a grenade and rifle attack that killed two officers and wounded 14 soldiers in Kuwait in 2003 during the opening days of the war.

Akbar, 34, a Muslim, told investigators he staged the attack because he was upset that American troops would kill fellow Muslims. He was condemned to death.