Suspect Roman G was arrested after the vicious attack, in which a pupil entered the school in Chelyabinsk and began 'randomly beating up his peers'.
A girl was rushed to hospital in serious condition and was undergoing surgery to save her life after she had her throat cut and was hit on the head with a hammer.
A second girl was also undergoing emergency surgery, and several more were injured during the attack.
Hours before the incident he had posted a rant on social media in which he said 'Putin has enslaved the population', accusing the dictator of 'Nazism'. Investigators are still trying to understand the motive for the brutal attack.
Comment: It sounds like the child, for whatever reason, had consumed Western propaganda and that apparently had a significant influence.
Notably, a number of recent would-be-assassins had, too: Trump 'Safe And Well' After ANOTHER Assassination Attempt, Man With 'AK' Rifle Arrested - Caught Targeting President as he Played Golf
News outlet Baza reported that the suspect 'came to school all in black in the middle of the first lesson, but did not go straight to the classroom, but walked past and went towards the toilet.
'A few minutes later, he ran screaming into the classroom where the Biology lesson was taking place and started waving a hammer.
'First, he hit one of the girls on the head, then the teacher.
'After that, Roman hit another girl and a boy, ran out of the classroom and ran down the corridor.'
The suspected attacker, named as Roman G, was ultimately detained by the National Guard at the remedial School number 68 and taken to a psychiatrist.
Four people were initially reported to have been injured, including a 13-year-old girl who is expected to be placed into an induced coma.
The seriously wounded girl named Valeria E was reportedly undergoing surgery in an attempt to save her life.
All four injured during the rampage - including the teacher, two girls and a boy - were taken to hospital.
Biology teacher Nina Shoshina, 57, was wounded as she tried to overpower the boy and protect her children at the school in Urals city Chelyabinsk.
The teacher said from hospital that the attacker 'ran into the Biology room five minutes before the end of the lesson.
'He was holding a gun and a hammer. He didn't say anything, he just screamed.'
Lenta reported that the boy had brought an air gun into class.
'I immediately started screaming to stop him. I ran up to him, but the girls were a little faster,' the teacher added.
'He hit both of them on the head with a hammer, then I got hit on the arm, shoulder and head.'
A student in another class told of the horrific incident.
'We were sitting in physics class and heard screams in the hallway on the second floor,' said an eighth-grade student.
'It was almost 9am. We wondered what was going on.
'The teacher came out and saw that everyone was covered in blood. She tried to protect her classmate from the blow, but it didn't work.
'There was blood in the hallway and in the toilet. They then escorted us out of the building.'
A grandmother of one of the wounded girls said: 'He went into the classroom, sat there for a while, came out with a gun, an axe, a knife - and this is what happened.
Other reports said he was armed with a hammer not an axe, and was detained in the toilets.
The suspect was also alleged to have been taking part in a sinister online suicide game which involved wounding people before taking his own life.
Investigators said they would look into the claims as they probe the organisation of security and compliance with school regulations.
The Investigative Committee has begun criminal proceedings for negligence and attempted murder, TASS reports.
Hours before the attack, the student posted on Telegram about the so-called 'slavery' of the school system.
'School is designed to make young children slaves and distract them from the truth of our government,' he wrote, according to Lenta.
'In schools they instil what is good and what is bad, but in reality there is no good and bad,' he wrote.
'And there is no hell. Our great nation needs freedom of speech.'
Comment: Does he mean like over in the US?
The boy's father said he was more interested in playing Minecraft, but that he had been bullied at school, with classmates spitting on him and 'morally destroying him'.
Regional governor Alexei Texler said: 'A schoolboy attacked other pupils and teachers.
'There are victims. They are hospitalised, all necessary medical care is being provided.'
He stressed: 'An investigation is underway. A big question is how the student brought a hammer into the school. Why did the security not react?'
And this smells American produced.