An internet troll admitted threatening to kill 200 US citizens in Facebook posts which led thousands of children to stay off school.
Father-of-one Reece Elliott, 24, of Fossway, South Shields, South Tyneside, went on a tribute site for a 17-year-old Tennessee girl who was killed in a car accident and left a series of terrifying messages under an assumed name.
With sensitivities heightened in the US following the Newtown shooting which saw 20 children and six adults shot in an elementary school, 3,000 pupils in the Warren County area missed school the next day, Newcastle Crown Court heard.
Security was stepped up at schools across the area, as the authorities implemented "lockdown" with armed guards on duty and restricted access to sites.
Elliott appeared at court dressed in a grey top and admitted one count of making a threat to kill and eight of sending grossly offensive messages.
He has been held in custody since his arrest in February.
Using a false name, he wrote on the RIP Caitlin Talley page: "My father has three guns. I'm planning on killing him first and putting him in a dumpster. Then I'm taking the motor and I'm going in fast.
"I'm gonna kill hopefully at least 200 before I kill myself. So you want to tell the deputy, I'm on my way."
Using the same pseudonym, Elliott then posted the threats about driving into school. He said: "I'm killing 200 people minimum at school. I will be on CNN."
Judge James Goss QC said sentencing would be delayed until pre-sentence reports could be taken. He said: "You will remain in custody until the sentence hearing, as I'm sure you will appreciate the offences are serious matters. A prison sentence is of course the inevitable sentence in respect of these offences."