Boduka Mudianga studied art and design at Southgate College
An 18-year-old student was caught unawares when his attacker flicked open a knife and fatally stabbed him during a fight, the Old Bailey has heard.
Boduka Louis Mudianga, from Enfield, north London, was attacked in nearby Edmonton, when he and a friend became involved in a clash on 21 January.
Mr Mudianga, died after suffering a single stab wound to the chest.
Kevin Lewis, 18, from Edmonton, denies murder and wounding with intent. He has claimed he acted in self-defence.
Mr Lewis was 17 at the time of the killing, the court heard.
Mr Mudianga, known among friends as Louis Boduka, was an art and design student at Southgate College.
It is not clear what history there was between the teenagers, but there was a shout of "that's him" from the bus before Mr Mudianga and his friend got off, the jury was told.
The victim first punched Mr Lewis's friend before the accused flicked open a knife and stabbed Mr Mudianga in the chest "without warning", the court heard.
Mr Lewis was hit in the face by the victim's friend, after which he stabbed Mr Mudianga's friend twice, the court was told.
The friend was left with injuries to his chest and upper arm.
Mr Shorrock, prosecuting, said: "In response to a single punch with a clenched fist towards his friend, the defendant produced a knife without a word and punctured a blow to the victim's chest.
"Even if the defendant perceived an imminent attack upon him or his friend, his reaction was wholly disproportionate and excessive.
Mr Lewis "was prepared to use a knife in such a way to kill or in the very least cause serious harm," Mr Shorrock said.
The court heard Mr Lewis told police that he "deeply regretted" the incident but he had "instinctively lunged with the knife" for "fear for his own personal safety".
The accused also said he did not know where the men were stabbed and that he "panicked" and threw away the knife.
Days later Mr Lewis was arrested at a hotel in Northamptonshire, and the court heard a ticket to Kingston, Jamaica, had been booked in his name.
The weapon has not been found and Mr Shorrock said there was "no suggestion" that Mr Mudianga and his friend were armed.
The trial continues.