The juvenile allegedly accessed Google Classrooms at Newtown High School in Connecticut and used "racial epithets in an abusive and disruptive manner," police said.
He made the comments while campaigning in Pennsylvania Saturday and has suggested the election will be decided in the high court in the days or weeks after November 3.
Sandy Hook Elementary school students were dismissed for the day following the threat.
The number of children killed by gunfire in the United States since the 2012 mass shooting at Sandy Hook Elementary School is greater than the total of U.S. soldiers killed in overseas combat since 9/11, according to a Department of Defense report.
"Obviously, this is why we have unintentional shootings involving children."
"It's a pleading, not a protest."
The guilty plea is an illustration of how unhinged conspiracy theorists latched onto the Newtown shooting and harassed the family members of victims.
The cyclists are riding with their backs to Congress this year to protest lawmakers not passing measures to reduce gun violence.
One senator compared Trump's opportunity to enact gun laws to President Richard Nixon's visit to China in 1972.
The U.S. outranked China, Japan, Germany and the U.K.—combined—in firearm assaults.
See if you can catch the message the first time you watch the nonprofit's new video.
Sandy Hook families argue the rifle used in the 2012 school massacre should not have been entrusted to civilians.
Radio host Alex Jones repeatedly has called the 2012 Connecticut massacre a "hoax" involving child actors.
The families argue that the sale of the military-style rifle used in the 2012 massacre violated Connecticut's law.
The 'Newtown' filmmakers are showing support to Aurora victims facing payment of $700,000 in legal fees.
A lawyer for the gun maker argued Monday that it's not the role of a court or jury to decide who can own AR-15 rifles.
Society is always threatened by individuals like the Orlando shooter, Omar Mateen, who have corrupt hearts and the malicious intent to purify the world of sin.
The United States, with less than 5 percent of the world's population, has about 35 to 50 percent of the world's civilian-owned guns.