The gunman who killed eight people at a FedEx Corp. facility in Indianapolis in April was likely not motivated by bias or racism, investigators said Wednesday.

Investigators interviewed more than 100 people, executed more than 20 search warrants and combed through 175,000 computer files belonging to the shooter for months before determining the shooting wasn’t a hate crime.

“The shooter did not appear to have been motivated by bias or a desire to advance an ideology,” said Paul Keenan, the Indianapolis FBI’s special agent in charge, at a Wednesday press conference.

Nineteen-year-old Brandon Scott Hole, who was white, killed eight people, including at least four members of the Sikh community, raising questions about his motivation. The shooting occurred just weeks after a white gunman killed eight people at three Atlanta-area massage parlors, including six women of Asian descent and deepened the nationwide conversation about racism and a recent rise in anti-Asian bigotry.

The Indianapolis shooter sought to prove his masculinity to himself by experiencing what it was like to kill other people and then die by suicide, investigators determined. He targeted the FedEx facility because he had been employed there and knew the location and work patterns. He had thought about alternative sites to attack in the roughly nine months he spent planning, they said.

“This was an act of suicidal murder in which the shooter decided to commit suicide in a way which he believed would demonstrate his masculinity and capability while fulfilling a final desire to experience killing people,” Special Agent Keenan said.

Police have identified 19-year-old Brandon Hole as the suspect in a shooting that killed eight people and wounded several others at an Indianapolis FedEx facility in mid-April. Hole was a former FedEx employee, police said. Photo: Jeff Dean/Agence France-Presse/Getty Images The Wall Street Journal Interactive Edition

The shooter had been questioned by authorities previously. In March 2020, his mother reported that she was concerned he would attempt “suicide by cop” and authorities confiscated a shotgun from him and temporarily committed him to a local hospital. They found no indication he had committed a crime, and he was released. Unknown is how he was able to buy firearms after the confiscation.

He worked at the FedEx facility for two months in late 2020 and bought rifles used in the shooting in the summer and fall of that year, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Investigators found 200 World War II Nazi-related files on the shooter’s computer but he didn’t appear to have those files for overtly racist purposes.

Separately, investigators found that the gunman in the Atlanta spa shootings wasn’t motivated by racism but instead by sexual compulsions.

Write to Ben Kesling at benjamin.kesling@wsj.com