The person who shot and killed eight people and injured five others at the FedEx Ground Facility near the Indianapolis International Airport on April 15, acted alone and no one else had any prior knowledge of the events, said a reports from the Indianapolis Metro Police and the FBI.

Investigators announced Wednesday, that they had completed their joint investigation.

Unfortunately sometimes, even after months on deep investigations, not only by us but by our partners, the why is still unknown,” said IMPD Chief Randall Taylor.

Brandon Hole, 19, killed himself after shooting eight of his former co-workers shortly after 11 that night.

“The shooter’s attack did not appear to have been motivated by the need to address perceived injustices or to advance an ideology but was an act of suicidal murder. This is a term intended to convey the murders were a function of a primary desire for suicide,” read a news release from police.

After 120 interviews, 20 search warrants and examining over 150 pieces of evidence, police concluded that the shooting was not racially motivated.