Hakim Sillah was killed after a fight broke out during the event at the Youth Offending Service at Uxbridge Civic Centre
A boy aged 18 was stabbed to death in a fight while attending a knife awareness course in the town hall of the Prime Minister's constituency.
Hakim Sillah died as youths clashed 'in the blink of an eye' after a blade was brought into a Youth Offending Service office.
Last night his mother was said to be 'broken' after dropping him off at the Hillingdon Council headquarters in Uxbridge, West London, for the course she hoped would steer him away from violence.
Just 50 minutes later, the engineering student was critically injured in the fight between teenagers thought to have been referred there due to a history of carrying weapons. Paramedics tried to save Hakim's life on Thursday, but he was pronounced dead in hospital an hour later.
A 17-year-old boy, who bravely tried to intervene, was slashed across the ear, but not seriously injured. Last night police were questioning another 17-year-old arrested on suspicion of murder.
Yesterday it emerged that those attending the event were not searched for weapons despite council staff raising concerns about blades being smuggled into the building previously. Staff said they had called for knife arches to be installed but nothing had been done.
A council worker said: 'We need serious action. I am thinking of resigning. A while ago, a man pulled a knife on a colleague. You can't have people bringing knives into the council. We need knife arches.'
Paramedics tried to save Hakim's life on Thursday, but he was pronounced dead in hospital an hour later
Forensics officers were seen outside the local Youth Offending Service after the stabbing in Uxbridge
Another said: 'We are all in total shock. We need more protection. The violence is coming off the streets and into public buildings.'
Friends of Hakim reacted with anger yesterday. Selina Clarke, 18, who went to school with him, said: 'I am more angry it happened in a knife crime meeting and they were so careless not to check.
'You would think they would do security checks, especially given the people involved in it. They cannot have been searched properly otherwise they would have seen the knife. It is so simple to put checks in place like a pat-down