Thomas Devlin, 15, was knifed five times in the back after two men jumped him on a north Belfast street late last night.
A friend, aged 18, was also injured, although not seriously, while a 16-year-old boy managed to escape.
As murder squad detectives hunted for the killers, Thomas's mother, Penny Holloway, said her family was shattered.
"He was such a lovely, good-natured, bright and kind-hearted boy," she said. "For his life to be snuffed out like this is unbelievable. We're just devastated."
Thomas, a student at Belfast Royal Academy, was a talented musician who played the horn at school.
He spent Wednesday night playing computer games at his home in the Somerton area, an affluent district of the city.
One of his friends planned to stay over, so they decided to go out for food.
"They all went down to the Esso Garage at Fortwilliam to get sweets and crisps and Coke," Mrs Holloway said.
"These guys were obviously following them. They were jumped from behind and stabbed in the back.
"Thomas was stabbed five times and they intended to kill him. It's come to something when a boy can't even walk up the street to his own home."
Mrs Holloway, who works in industrial relations, and her broadcaster husband Jim Devlin, have been trying to comfort their two other children.
A pet dog, Rosie, who followed Thomas everywhere, has been searching the house looking for the boy, they said.
Mrs Holloway also said a doctor tried desperately to stem the bleeding as her son lay dying.
"He had his whole future in front of him," she said. "I just can't believe that someone would attack him and intend to kill.
"Police have told us they don't have a motive. If anyone knows about this please, please give police that information."
Three people were later arrested by detectives investigating the murder.
Two men and a male juvenile were being questioned about the killing of the teenager, said a police spokesman.
The murder, just days after a 15-year-old girl was subjected to a sadistic double rape in west Belfast, horrified public representatives.
Alban Maginness, an SDLP Assembly member for the area, claimed violence was now rife on the city's streets.
"This is an appalling act and my heart goes out to the mother, father and rest of the family," he said.
"Leaving aside sectarian and paramilitary activity there has been an increase in violence.
"Coming so soon after the rape it paints an awful picture of the city."