“All he felt was anger, and all he saw in that park were guns.”

Darkness was a part of Steven Nelson Lopez’s life long before last weekend, when he allegedly opened fire into a crowd of protesters in Louisville, Kentucky’s Jefferson Square Park.

The 23-year-old was raised by his grandparents in what some describe as a “rough” part of town. He was diagnosed with ADHD, but Lopez’s grandfather, Michael Arnett, believes he’s schizophrenic.

About four and a half months ago, Arnett told ABC News his grandson packed his bags and went to live at the park.

Lopez’s grandfather said he’s “exhausted” and “mentally strained” by his grandson’s actions, and it pains him to know it all stemmed from a “mental health issue” that should have been treated.

Organizers of the protests said on Facebook he caused trouble at the daily gatherings. Police said he was arrested twice in the past month for assembly-type offenses.

Jeff Gill, who runs a homeless outreach program and has known Lopez for years, said he was taking medicine for schizophrenia and ran out. He believes the lack of medication turned him erratic.

On June 27, Lopez was seen looking dazed at the Louisville park, wearing baggy shorts, no shirt and loose hair. Gill checked up on him that day and knew something was off.

“He had his shirt tied around his arm and a pained look on his face and he kept mumbling, ‘It’s broken,'” Gill said of Lopez.

He spent most of the day hovering around the protesters and at one point, caused a group of men to get angry and “beat him up,” Gill said.

It was then that he was asked by security to leave the park, but moments later he emerged wearing a new set of clothes, a ponytail, a mask and carrying a gun that he took from an armed protester, according to the Louisville Metro Police Department. That’s when he allegedly opened fire, killing Tyler Gerth, 27.

“He wasn’t aiming for Tyler,” Gill said. “I’m not justifying anything that Mr. Lopez did. It was horrendous, a tragedy, it could’ve been prevented. But his mindset on that day was one of chaos, and all he felt was anger, and all he saw in that park were guns.”

On the day of the shooting, the American Freedom Fighters, an armed nationalist group, had threatened to show up at the park, saying on social media that they had the LMPD’s support. The American Freedom Fighters never materialized, but protesters were walking around the park openly armed, carrying large guns and even wearing bulletproof vests.

“LMPD personnel did reach out to organizers of this group planning to counter-protest this weekend to get information for our planning purposes, but in no way did LMPD express support for any disruptive actions being taken by this group or any other. We support everyone’s right to free speech and expression. Our role is to make sure that takes place in as safe an environment as possible,” the LMPD said in a statement to ABC News.

In a video of the shooting captured by Louisville local Maxwell Mitchell and shared with ABC News, men holding guns can be seen running from Lopez as he opens fire, while others form a barrier around the two victims as police apprehended the shooter.

One week before the shooting, police arrested Lopez, along with various protesters, for assembling at the park, and took their guns. In a statement, the police department confirmed that the gun they confiscated from Lopez is still in their possession, and is not the one he allegedly used in the shooting that killed Gerth.

Still, many are wondering how Lopez was able to purchase a firearm in the first place, when he was homeless and had a history of mental health issues.

“Many of the homeless have weapons,” Gill said, speaking of those who sleep on the streets rather than in institutionalized shelters.

Gill has seen cases like Lopez’s before, which is why his work is so crucial to him and his community.

“My main focus is helping those in homelessness, but what leads to homelessness is often addiction and mental health,” he said.

Lopez pleaded not guilty Tuesday to murder and nine counts of wanton endangerment. His next court date is set for July 8.