The teen, who has interim name suppression, is on trial at the High Court at Dunedin defending a charge of murder.
The defendant says he was acting in self-defence when he stabbed 16-year-old Enere Taana-McLaren on May 23 last year.
Yesterday, Tyler Gemmell, who was working as a security guard at the bus hub on the day, described the parts of the scuffle he saw.
He told the jury that after the defendant stabbed Enere he heard the defendant say "that’s what you deserve".
Under cross-examination from Anne Stevens KC the witness remained sure that was what he heard.
However, he was unsure about much of his other evidence and could not recall other words exchanged between the boys.
He gave his statement to police in the days after the event, which had shaken him, he said.
"There’s a possibility that a little bit of [the statement] could be wrong."
The court heard there were two security staff working at the time, but the other person was away changing his clothes.
Once Mr Gemmell saw the knife he tried to "de-escalate the situation with words".
"I’m not going to put myself in harm’s way when somebody has a weapon," he told the court.
Later he helped break the pair up.
He knew the defendant from his time working at the bus hub and thought he was friendly and polite.
"He used to come up to us at the bus hub and say ‘hello, how’s it going, how’s your day’."
A staff member at the defendant’s school also gave evidence yesterday.
He told the court that earlier on May 23 the defendant was part of a group of boys who were allegedly vaping in the toilets.
The defendant was put into a room on his own while the other boys were spoken to.
When the staff member went into the room the defendant was wearing a sideways cap, which was not part of the uniform, and listening to rap music.
The staff member demanded the cap, but the defendant did not want to hand it over.
"He was aggressive in his manner toward me, he was agitated, he wasn’t happy," the witness said.
"I was getting concerned because of his agitation. He had never behaved like that with me."
The witness said the defendant "shaped up" to him, which he explained, under cross-examination, meant he turned side on.
The defendant had not advanced toward him or raised fists.
He had never had a student shape up to him before, but did not record the unique interaction in his notes of the event.
Mrs Stevens asked if he could be misremembering events since the murder charge had been filed.
The witness said he was sure he was not and recalled he was "worried about his own personal safety".
On leaving the room the staff member heard a loud noise and when he went back in, a chair was lying on its back.
He "assumed" the defendant had thrown the chair, he said.
Ultimately, he made the decision to have another staff member take the defendant home.
Justice Robert Osborne is presiding over the trial, which is expected to last about three more weeks.
felicity.dear@odt.co.nz , Court reporter
