Deputy Mayor Ray Lewis said some youths are growing up "angry"
There is "no magic solution" to the issue of violent youth crime in London, a conference has been warned.
Families who have lost children to gun and knife crime met at City Hall to talk about how to deal with the issue.
The summit came a day after Sharmaarke Hassan, 17, became the 15th teenager to be killed in the city this year.
Ray Lewis, the deputy mayor for young people, said we need to look at why so many children "are growing up angry, and disengaged from society".
The parents of murdered teenagers James Smartt-Ford and Kiyan Prince were among those at the conference.
And representatives from the Metropolitan Police, youth charities and members of the London Assembly also attended.
Police seized more than 200 knives in the past two weeks
Addressing the summit, Mr Lewis said: "There is no magic solution to the terrifying spate of teenagers being murdered by knife and gun crime.
"It is also imperative that we look at why so many young men and increasingly women are growing up angry, and disengaged from society."
Mr Lewis also stressed the importance of stop and search operations by police, which were stepped up this month, to spot knives and guns.
He added that there was a need to find creative outlets for teenagers and to "treat the profound contempt for society and lack of self-respect that has alarmingly developed in some of our young people".
Deputy Mayor for policing, Kit Malthouse, said: "The long-term solutions to youth crime are complex and will require a wholesale cultural shift."
On Thursday, Metropolitan Police Commissioner, Sir Ian Blair, revealed that in the past two weeks about 200 knives were seized and 200 people were arrested during stop and search operations across London.