Barry Mizen said people should look at the choices they make in life
More than 500 people have packed into a church for a memorial service for 16-year-old Jimmy Mizen.
Jimmy, who celebrated his birthday a day before his death, was killed in an attack at the Three Cooks bakery store in Lee, south-east London, on 10 May.
At the service, the mayor of Lewisham, Sir Steve Bullock, said the loss of a young person is not only what they were but what they could have gone on to do.
Jake Fahri, 19, of Lee, has been charged with Jimmy's murder.
Crying as they stood under umbrellas in the rain prior to the service, Jimmy's family were surrounded by hundreds of friends and well-wishers.
Jimmy's parents talk about their grief
Jimmy's father, Barry Mizen, said: "It does not have to be like this.
"Perhaps we all need to look to ourselves and look to the values we would like and our responses to situations in our life.
"Sometimes we might be drawn into certain ways of our living. It is our choice but change has got to come from all of us."
Jimmy's mother Margaret urged people not to blame the family of the suspect in her son's killing.
"Anger breeds anger, and bitterness will destroy my family if I'm not careful - and I won't allow that to happen," she said.
Mrs Mizen said her son was born on the day of the FA Cup Final in 1992 and described him as a "gorgeous baby" .
Jimmy Mizen died the day after his 16th birthday
Jimmy's brother, Danny, 30, told the congregation that it was a source of comfort that two of his other brothers, Harry and Tommy, were with Jimmy when he died.
He described Jimmy as his "little hero".
After the 45-minute service, the Mizens led the crowd of mourners down the road, which police closed for the service, to the bakery where Jimmy was killed.
Prayers were said and Mrs Mizen laid lillies, symbolising love and peace, among the other collections of flowers and tributes at the scene.
Described as a "gentle giant", Jimmy was 6ft 4in (1.92m), and a committed Christian.
He leaves behind his parents and six brothers and two sisters - Tommy, Joanne, both 35, Danny, 30, Billy, 28, Bobby, 24, Samantha, 21, Harry, 18 and George, eight.
Mr Fahri is due to next appear at the Old Bailey in August.
Jimmy was the 13th teenager to be killed in London this year.