(CNN) Koeberle Bull got on Facebook and saw several racist, cruel messages that used the N-word and wished death on her three African-American children.

She didn't know the white man who had messaged her -- she lives in New Jersey, and he appeared to live in Kentucky -- but he had a gun in his profile photo, so she decided to call police in Kentucky and report him.

"I was in shock, I was disgusted, I was angry and hurt," Bull said.

Little did Bull know that her call, and a follow-up police investigation, prevented what police say could have been a mass tragedy.

On Thursday, after speaking with Bull, Kentucky State Police went to interview Dylan Jarrell, the Lawrenceburg man who allegedly messaged her. Police say they found him backing out of the driveway with a firearm, a collection of ammo, a Kevlar vest and a detailed plan to attack local schools.

"This young man had it in his mind to go to schools and create havoc," state Police Commissioner Rick Sanders said. "He had the tools necessary, the intent necessary, and the only thing that stood between him and evil -- between him in a school doing evil -- was law enforcement."

These harassing messages led Koeberle Bull to call police.

Jarrell, 21, was arrested and charged with two counts of second-degree terroristic threatening and one count of harassing communications, police said.

His public defender, Amy Robertson, would not comment on the specifics of the allegations.

"These cases are very complex and often have many sides to them. It is not uncommon for it to take a long time for all the facts to come out," Robertson said. "I ask that you not jump to any conclusions and give me time to do my job."

Questioned over alleged threats to a school

Police said they found evidence of a "credible and imminent threat" to nearby Shelby and Anderson County schools.

Authorities said they obtained a search warrant for Jarrell's home and electronic devices. Jarrell's internet history included a search for how to carry out a school shooting, police said, and the FBI questioned him in May over social media threats to a school in Tennessee.

Kentucky State Police said Jarrell had more than 200 rounds of ammunition, a 100-round high capacity magazine and a detailed plan of attack. There may be additional charges, Sanders said.

Court records indicate Jarrell was arraigned Monday and entered a not guilty plea with Robertson. His bond was set at $50,000.

Jarrell is being held at the Shelby County Detention Center and has a preliminary hearing in Anderson County scheduled for November 1, according to court records.

'I didn't know what he was capable of'

Police say Dylan Jarrell had a weapon, ammo and a detailed plan to attack Kentucky schools.

Before she called police, Bull posted a screen grab of the racist message on Facebook.

"Anyone who thinks racism doesn't exist, this is what I woke up to in my inbox this morning," she said in her post. "Let's share this and make this guy famous please."

She tried to message Jarrell but he had blocked her, she said. With help from her friends she was able to find him and call police -- first in her hometown and then in Kentucky.

Now, days later, Bull's Facebook page is full of messages of praise, thanking her for preventing what could have been a tragedy.

"People are reaching out and calling me a hero and calling me a guardian angel, but I was just being a mom," she said. "I was just being a mom who wanted to protect her kids."

As a precautionary measure, Anderson County Schools were closed on October 19, and Shelby County Public Schools suspended activities at Shelby County High School, too.

On the Anderson County Schools website , officials thanked security officials and first responders "who eliminated a threat to AC students and staff, worked countless, tireless hours to ensure our safety and humbly take no credit for their heroic actions."

At a press conference, Sanders thanked Trooper Josh Satterly, a "humble, dedicated trooper" who took Bull's report and followed up with other agencies to investigate.

Bull said she is grateful that Satterly validated her concerns, despite her suspicion that her call would lead nowhere.

"I thought, 'they're not gonna care about my three black kids from New Jersey,' and this community genuinely did care about my kids," she said.

"If you see something, say something -- I never took that as seriously as I do now, and now I know that it matters," she said.

"I didn't know what he was capable of."