Mary Moody said Frederick was a much-loved son
The mother of a teenager stabbed to death after a row over a water fight has spoken of the "senseless and meaningless loss."
Frederick Moody Boateng, 18, was killed near his home in Lambeth, south London, on 17 July.
His mother Mary Moody, spoke as about 300 people gathered for a vigil at the scene of the murder on Guildford Road.
A man was arrested on Tuesday in connection with his death and continues to be questioned by police.
A 16-year-old who was arrested on the night of the incident has been released on bail until mid-August.
A line of water guns were left on Guildford Road along with more than 50 bunches of flowers and notes from friends.
Ms Moody said he was a much-loved son who "filled our lives with cheerfulness, laughter and joy".
"We are extremely devastated by this tragic, senseless and meaningless loss at the tender age of 18," she added.
"We draw strength from the love and care he lavished on us. We take courage from the memories of a good man who stood out for his good character."
Church ministers from across south London attended the vigil and several of them called for an end to knife crime.
One said: "We as a society have to rally against knife and gun crime. Our young people must stop taking the law into their own hands."
The family led the mourners on an "anti-knife crime march" in memory of Mr Moody Boateng.
Many of them donned orange T-shirts for the third-of-a-mile (480 metres) walk, to Stockwell Tube station and back, as it was the teenager's favourite colour.
Two of his college friends held up a large banner, with the words: "In memory of Freddie! Please stop the knife crime."
Mr Moody Boateng, a former business student at Kingston College, became the 21st teenager to die in violent circumstances in London this year.