(ANSA) - SKOPJE, FEB 21 - In an anti-terrorism operation that stemmed from an FBI tip, police in northern Macedonia arrested a 20-year-old young man who had an arsenal of firearms, explosives, and other military equipment in his home and who online threatened a massacre, a mass shooting in imitation of some carried out in the United States, and claimed to be mentally ill. The alert, police say, was raised by the FBI, which detected threats on the network coming from a profile called 'Discord,' and made the report through the U.S. Embassy in Skopje. The operation was, coordinated by the prosecutor's office against organized crime. In the home of the young man, a resident of Mala Rečica, an Ak-47 Kalashnikov automatic rifle with magazines, several pistols of various calibers with hundreds of rounds, bulletproof vests, knives, and electronic equipment were seized. An 89-year-old man, also a resident of the area, also ended up in the meshes of justice for the crime of unauthorized manufacture, possession and trade of weapons and explosives. (ANSA).