A G4S security firm worker has been found guilty of blackmailing the firm for £1m with a bomb threat.
Daniel Garland, 19, from Chester-le-Street, sent an anonymous letter to the firm's Thornaby depot in January claiming he had attached bombs to vans.
He admitted a bomb hoax but denied it was blackmail saying he was trying to get back at two "bullying" colleagues.
Jurors at Teesside Crown Court found him guilty of blackmail. He will be sentenced at a later date.
The trial heard how Garland's letter demanded £1m or he would detonate mini bombs he claimed to have fitted to several G4S vehicles and an employee's car.
He also threatened to harm a newborn baby and her mother if his demands were not met.
'Bullied at work'
More than 100 police officers joined a major inquiry across four force areas. Cash-in-transit vans were recalled to the depot to be searched and the security giant's losses were put at £15,000.
The note mentioned a previous armed robbery on a van and the letter's author claimed to be the raider responsible and named two G4S staff who he alleged had passed on information.
Garland said in his defence he had been bullied at work and the motivation for writing the letter was merely to get the two named colleagues into trouble, and perhaps a move away from his section.
A jury deliberated for more than five hours and convicted him of blackmail, knowing the menacing letter would cause G4S a loss.
He was cleared of an alternative blackmail charge of intending to gain the £1m.
Recorder Euan Duff remanded him in custody and warned him he faces a "significant sentence" on 29 September.