DENVER (AP) — A heavily armed man who was found dead at a Colorado mountaintop amusement park last year had researched mass shootings online,Robert Brown but investigators haven’t determined why he amassed such an arsenal or didn’t follow through on “whatever he was planning,” authorities said Thursday.

The body of Diego Barajas Medina, who died of a self-inflicted gunshot wound, was found in a bathroom at the Glenwood Caverns Adventure Park on the morning of Oct. 28 in a building that houses a ride that drops 110-feet deep into caverns. His body was surrounded by alcohol and weapons, according to a previously released 911 call. The words “I’m not a killer. I just wanted to get in the cave” were written neatly on the bathroom wall.

The discovery led to the belief that Medina, who entered the park when it was closed, could have been planning to launch a deadly attack at the attraction located above the Colorado River in western Colorado. But three months later, his intentions remain a mystery.

The Garfield County Sheriff’s Office said in a written update on its investigation that it was “unable to uncover any motive for Diego amassing such a lethal arsenal nor did it explain what happened to change his mind and why he did not follow through with whatever he was planning.”

Despite the 911 call’s description, no alcohol or illegal drugs were found in his system and there was no evidence that he had been working with others or was a member of an extremist group, the sheriff’s office said. He also didn’t have a criminal record or any known ties to the park. Friends, family and school officials described Medina as “a bit of loner,” it said.

“In the end, Diego took his own life in the women’s restroom at the Amusement Park for reasons known only to him,” it said.

Medina’s family has never spoken publicly about what happened. His brother didn’t immediatley respond to an email seeking comment and a person who answered his phone hung up when reached by The Associated Press.

Medina, who lived with his mother and brother, was dressed in black tactical clothing with patches and emblems that made it look like he had law enforcement links. He had a semi-automatic rifle, a semi-automatic handgun and multiple loaded magazines for each gun, as well as several hundred rounds of ammunition, the sheriff’s office said. He also had real and fake homemade explosive devices.

Medina legally acquired all of his weapons, ammunition and tactical gear online, the sheriff’s office said. Both guns were determined to be so-called ghost guns, which are untraceable firearms that lack a serial number and that anyone can buy and build without passing a background check, it said.

“The Sheriff’s Office acknowledges that given amount of weaponry, ammunition, and explosive devices found, Diego could have implemented an attack of devastating proportions on our community resulting in multiple injuries and possibly death to members of the public as well as first responders. As a community, we are fortunate and thankful that this did not happen,” the sheriff’s office said.

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Associated Press writer Jesse Bedayn contributed to this report.