It was reported that the 15-year-old arrived at school before the first lesson and stabbed his history teacher in the neck, fatally injuring her.
He then entered a classroom where he killed a student and injured two others before escaping via the window.
The attacker was arrested two hours later by the police. The incidence took place in Stolbtsy, Belarus.
It was gathered that the teenager deleted his social media presence the day before the killings.