Robert Knox's family speak of their pain at his death
The parents of a young actor stabbed to death in London have paid tribute to their "kind and thoughtful" son and urged people not to carry knives.
The father of Rob Knox, 18, who was stabbed to death in a fight outside a bar in Sidcup, said he was "always the first person to stand up to wrong".
Earlier Maggie Knox said her grandson, who had a small part in the new Harry Potter film, was a "big teddy bear".
A 21-year-old man has been arrested on suspicion of murder.
Mr Knox was killed, and three others stabbed, in a fight outside the Metro Bar in Station Road with a man who was armed with two knives.
'Touched many lives'
His father read out a statement to journalists on Sunday which said: "It's impossible to convey the sadness and loss that we all feel but we now realise Rob touched many people's lives.
"Rob was happy, outgoing and a fun person to be with. He was the social hub of his large circle of friends."
Colin Knox said his son "touched many lives"
"Rob always put everyone before himself, was always the first person to stand up against wrong. He achieved so much in his short life."
Mr Knox added: "With knives there are no winners and there are only losers.
"If you are a person that carries a knife, think about the consequences before you carry the knife because if you carry a knife there's an intention to use it.
"And please don't do that for the sake of my son."
Mr Knox said if the media attention surrounding his son's killing encouraged people to stop carrying knives his death would not have been in vain.
His grandmother Maggie Knox told the BBC she adored Rob.
She went on: "I hope people listening who have teenagers, boys especially, take note - check what they're carrying in their pocket.
"Try, at least try, to put a stop to this dreadful thing. They would never want it to happen to them."
Mr Knox's uncle, John Knox, said his nephew was polite and playful, and "never took liberties with anyone".
He said he could not understand why people felt the need to "stroll around" with knives and called on the government to get "firm" with them.
"It makes them feel big I suppose, in some way they must be lacking internally where they feel the need to carry them," he said.
He also disagreed with comments about knife crime made on Saturday by Sir Aynsley Green, the Children's Commissioner for England.
Sir Aynsley said new measures, such as police officers using hand-held and walk-through metal detectors, could antagonise the young.
But John Knox said rather than "treat them nicely", those caught carrying knives should be sent to jail.
"Don't mollycoddle them, if they want to get that type of action going, bang them up, bang them up for five years," he said.
Rob Knox (right) was stabbed to death on Saturday
"This wouldn't happen if people were firmer with them. It'll go on and on and on."
Mr Knox is the 14th teenager to die violently in London this year. Police said they were keeping an open mind over his death but they did not believe it was gang related.
Since his death, family and friends have been laying flowers at the scene of the attack, and paying tribute to Mr Knox.
The teenage actor had won a part as one of Harry Potter's fellow pupils in the new film, The Half Blood Prince, which has finished filming.
In the incident in the early hours of Saturday, a 16-year-old was stabbed in the chest but he has since been released from hospital.
A 20-year-old who sustained a hand injury has also been discharged, while a 21-year-old stabbed in the neck is reported to be in a stable condition in hospital.
The 21-year-old man who is being held on suspicion of murder suffered facial injuries and was arrested after being released from hospital.