CLEVELAND, Ohio — A Toledo man on Thursday admitted his guilt in a plot where he and his girlfriend planned to use explosives and guns for a mass murder.

Vincent Armstrong, 23, pleaded guilty to conspiracy to transport or receive an explosive with intent to kill, injure, or intimidate any individual, and maliciously damage or destroy by fire or explosive. The FBI arrested him and Elizabeth Lecron in December for a plot they started forming in April, according to court records.

Both planned to attack an unnamed Toledo bar, and the couple bought a gun and parts for makeshift bombs, according to Armstrong’s plea agreement. The FBI previously said Lecron was also involved in a plot to blow up a pipeline in Georgia.

The couple was interested in mass murderers and cited diary entries and posts on the social media website Tumblr as evidence of the interest, according to federal prosecutors. Lecron even corresponded with Dylann Roof, a South Carolina man who killed nine worshippers at a church in 2015, authorities said.

Agents said the plot against a second-floor Toledo bar was halted after someone found Lecron’s diary and confronted them.

As the couple planned the attack, they also bought clothing to emulate the two shooters who opened fire at Columbine High School in Colorado in 1999, according to the plea agreement.

Armstrong entered his plea in front of U.S. Magistrate Judge James Knepp in Toledo. He faces between five and 20 years in federal prison. Prosecutors agreed to drop other charges a grand jury brought against him in January.

A sentencing date has not been set. Armstrong’s attorney Adam Nightingale said he had no comment on behalf of his client.

State and federal authorities investigated the couple for several months prior to their arrests. Someone filed a complaint with police in June 2018 that said Lecron and Armstrong expressed a desire to commit an attack, according to court filings.

Armstrong’s plea agreement says the couple met in February 2018, started dating a few months later and moved in together. It didn’t take long before Lecron shared her interest in mass murders and introduced him to the “True Crime Community,” which operated across several social media sites and glorified mass murderers, the agreement states.

Lecron used the Tumblr profile names “ligaturemarkings” and “charlestonchurchmiracle,” while Armstrong used “societysheretic," the agreement says. Their interest spread far beyond social media, as the couple visited Columbine High School in August 2018, the plea agreement states.

The pair referred to their planned attack as “D-day.” The idea was to use guns and explosives. Armstrong owned an AK-47 rifle, and they bought a shotgun and went to the shooting range to practice, the agreement states.

Lecron also showed Armstrong a website with instructions on how to make bombs, and Armstrong printed out the instructions. Armstrong also started buying pieces for the bombs, according to the agreement.

They agreed to tell others that they were merely “role playing” if they got caught, Armstrong’s agreement says.

Agents searched the couple’s home when they were in Colorado and found an AK-47, handguns, ammunition and end caps that Armstrong bought that can be used to make pipe bombs. They also found Lecron and Armstrong’s journals, which contained entries about a violent attack, prosecutors previously said.

During a separate search in December, when both were arrested, agents found guns, ammunition, a gas mask and instructions on how to build bombs, according to court filings.

Armstrong used the line about “role playing” when agents interviewed him, but later admitted the plan was real.

Lecron has pleaded not guilty to the conspiracy, weapons and violent crime charges she faces. Federal prosecutors said she talked about another attack, separate from the one with her boyfriend, to blow up part of a pipeline that she had called a “cancer.”

Armstrong’s guilty plea comes after Connor Betts, 24, opened fire in a popular entertainment district in Dayton on Sunday, killing nine people and injuring 27 others, officials said. Among the victims was Connor Betts’ younger sister Megan Betts.

The FBI has opened an investigation and said Betts explored “very specific violent ideologies” before carrying out his attack, according to the Dayton Daily News.

“This week should show all Ohioans the threats that are ever present in our communities,” Toledo police Chief George Kral said in a news release announcing Armstrong’s plea.

“With this plea, a dangerous potential mass murderer will be off our streets.”

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