Vladislav Roslyakov, 18, massacred 20 people with a shotgun and a homemade bomb packed with metal shards in Kerch last week, before killing himself.
And harrowing CCTV footage has now come to light showing the twisted teen stalking the hallways and murdering his schoolmates.
He is seen calmly walking into the building with a large bag over his shoulder, passing peers he may well have later turned his gun on.
Security cameras then captured the moment a huge blast ripped through the building as he detonated his deadly device.
Classroom doors are blown off hinges and shards of glass sent flying out into the street outside.
The shooter then pulls his weapon from his bag and begins his deadly rampage as terrified students panic in the chaos.
Roslyakov killed 15 teens and five adults before he shot himself dead.
Russian TV interviewed a friend of the killer who said he "hated the technical school very much because of the evil teachers" and "hinted that he would take revenge on them".
He wore black trousers and a white T-shirt – clothing that resembled the outfit worn by the Columbine high school attacker Eric Harris.
The 1999 high school massacre has led to dozens of copycat attacks and plots in the US and abroad.
Traumatised survivors relived the horrors they witnessed in the aftermath of the shocking bloodbath.
One told RT: “My friend was killed right in front of me. I saw her fall and simply stop moving.
“I saw boys dropping dead and blood spilling around.”
Student Semyon Gavrilov said: “I looked outside the classroom and there was a guy with a gun shooting everyone.
“I locked myself in the classroom hoping he wouldn't hear me.
“Ten minutes later the police with machine guns arrived.
“Four windows have been blown out in the corridor where the explosion was.
“There were bodies of the dead on the floor. The walls were charred.”
Anastasia Yenshina, a 15-year-old student at the college, told Reuters: “I came out and there was dust and smoke, I couldn't understand, I'd been deafened.
“Everyone started running. I did not know what to do.
“Then they told us to leave the building through the gymnasium.
“Everyone ran there… I saw a girl lying there.
“There was a child who was being helped to walk because he could not move on his own.
“The wall was covered in blood. Then everyone started to climb over the fence, and we could still hear explosions.
“Everyone was scared. People were crying.”
More than 50 people were also injured in the killing spree including several with metal pieces embedded in their bodies from the bomb blast.
At least 40 of those still remain in hospital.
Sources revealed Roslyakov’s nurse mother Galina was treating wounded ferried from the attack to a local when she learned her son was responsible.
Police arrived to interrogate her and she was said to have left with detectives.
A local source said: "She is confused and cannot explain her son's motives."
She was reported to have tried to kill herself when she found out her child was behind the massacre.
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