Two of the wounded were in a critical condition, Gurlek said on Tuesday.
The assailant was caught and their mother, father, and grandfather - who owned the weapon used in the attack had been detained, the minister said.
"When the security of our children is the issue, it is not possible for any negligence, any irresponsibility to be overlooked," the minister said on X.
"The circumstances under which the child obtained the gun used in the attack, the conditions of the weapon's storage, the parents' obligations regarding care and supervision, and allegations of bullying prior to the incident are being investigated thoroughly and from multiple angles," Gurlek said.
Images and video posted online showed a male figure walking on a street near the school with a rifle in his hands.
He was then seen running back from the same street.
Video outside the school showed police pushing away families and others outside the premises.
The motive for the attack was not immediately clear.
The local governor's office has said the attack took place about 8am at the Inci Uzmez Vocational and Technical Anatolian High School in the Turgutlu district.
Two deadly school shootings in April caused outrage in Turkey and prompted officials to bring in new security measures for the 2026-27 academic year, including tighter gun controls.
Before then, the country had not had a history of such attacks.
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