At a press conference, police said Auvinen had acted alone. They described him as a lonely individual with extreme opinions.
Chief Inspector of the National Bureau of Investigation Rabbe von Hertzen said the perpetrator had chosen his victims at random, all of whom have now been identified. They were six of the high school's students, the school principal and school nurse. The victims had sustained injuries to the upper body and head.
Some 69 rounds were fired during the incident. Auvinen had a total of 500 rounds in his possession. He had also tried to set the school ablaze.
Upon arrival at the scene of the shooting on Wednesday, police had ordered the perpetrator to surrender his weapon but he replied by firing at the officers.
Officers rejected criticism they had been slow to act at the school noting that the safe evacuation of students from the premises was their first concern.
Police added they had no advance warning that the incident would take place. Auvinen had left a suicide note in which he said goodbye to his family and reiterated his angst towards society.
The shooting incident had lasted some 20 minutes. Police discovered Auvinen next to his gun two hours later in a WC adjacent to the school's dining room.
At the police press conference, it was also revealed that the shooter was a registered member of the firing range at the Helsinki Shooting Club. A licence to own a firearm had been granted on the basis of his membership a few weeks ago.
A spokesperson for the club told YLE that Auvinen had only visited the club once to attend a one-hour training session.
Police expect to be able to wrap up their on-site investigation at the school late this week.