The man had been conscious for a few days, which had been interpreted as a sign of recovery. He was even interrogated for the first time by the police on Wednesday at the Näl hospital in Trollhättan.
"He was able to cooperate for a short while and could tell us his version of what had happened," police commissioner Thord Haraldsson tells Swedish Radio's local channel Väst.
Haraldsson explains that the teacher confirmed what other witnesses have said about the attack.
The teacher is the third victim of the attack, perpetrated by 21-year-old Anton Lundin Pettersson. Lundin Pettersson used a sword and had "racist motives" according to the police. The other two victims were a teaching assistant and a male student.
The attacker died later of the gunshot wounds he received during his apprehension.