Kansas City, Mo. ? Investigators might never know why an elderly Missouri man went on a deadly shooting spree at a Roman Catholic abbey and then killed himself, the Missouri State Highway Patrol said Wednesday.

“Short of someone coming forward with information we don’t have, we don’t really have any more sources to evaluate or check at this time,” Sgt. David Merrill said.

Initially, investigators focused on lingering bitterness from Lloyd Robert Jeffress’ 1959 divorce and an annulment granted by the church 20 years later as a possible motive for Jeffress’ rampage June 10 at Conception Abbey.

Jeffress, 71, shot and killed two monks the Rev. Philip Schuster, 85, and Brother Damian Larson, 62 and wounded two others before killing himself in the abbey’s Basilica of the Immaculate Conception.

The injured monks, the Rev. Norbert Schappler and the Rev. Kenneth Reichert, remain hospitalized in fair condition.

While the church has made no public comment on the annulment, Merrill said a review of records and interviews with Jeffress’ neighbors and family members turned up nothing.

Jeffress had been estranged from his family for years, investigators said. Neighbors at his apartment complex in Kearney said he rarely spoke to them.

A search of Jeffress’ apartment turned up a prescription for the anti-depressant drug Prozac, but investigators did not know whether Jeffress had been taking it.

Residents of the abbey were resigned to never knowing the reason for Jeffress’ rampage, spokesman Dan Madden said.

“It’s only human nature that we would like to know, but even if we knew, I don’t know if it would make it any less senseless,” Madden said.