Ntombi Bambisa's son Nkululeko Ndlovu was shot and killed at Phineas Xulu Secondary School last week.
His alleged killer, 18-year-old Grade 11 pupil Tshundzukani Mthombeni, was yesterday released on R1,000 bail by the Boksburg Magistrate's Court.
Mthombeni whose mother is a police officer, allegedly stole her firearm, took it to school and shot Ndlovu.
Mthombeni faces charges of murder, theft of a firearm and possession of an unlicensed firearm. His lawyer, Xolani Tshabalala, said he intended to plead not guilty.
"If my son was a bully, why was he not found with a gun?" Bambisa asked.
"Why was it the nice guy (who had a gun)? If my son bullied him, why did he not shoot him in the leg at least?
"Whatever happens, we will not seek revenge. Nothing will replace my son."
During the bail application investigating officer Warrant Officer Isaac Mashishi told the court that he had difficulty getting statements from eyewitnesses at the school as the principal and teachers did not want to put him in contact with pupils.
The two statements he had received were contradictory, he said.
"The statements say that on November 19, the deceased was not present when the applicant [Mthombeni] was beaten up at a bus stop. There was a Nkululeko Biyela, a friend of the deceased Nkululeko.
"On November 20 the Nkululeko who is alive went to the classroom with the dead one. While he was pointing him out, the accused pulled out the gun and shot at them.
"The other version is that he only shot them when the two assaulted him."
Mashishi said Mthombeni stole the key to the safe where the gun was kept and took the gun. A pupil at the school told Sowetan that Ndlovu 's friends had threatened fellow pupils, vowing to avenge his death.
Gauteng department of education spokesman Charles Phahlane said they had referred reports of intimidation to the police.
The case will resume on January 16 next year.