A teenager has been praised by police for trying to stop a fight in a council headquarters where a man was stabbed to death in Uxbridge, west London.
Hakim Ishmael Daba Sillah, 18, was attacked while in the youth offending service department at the Hillingdon Civic Centre on Thursday.
He was taken to hospital but died almost an hour after being stabbed.
A 17-year-old boy who was arrested on suspicion of murder remains in custody.
The Met Police said the victim’s next of kin had been informed.
The teenage boy who tried to stop the fight sustained a knife wound to his ear.
Det Ch Insp Noel McHugh described the attack as “an absolute tragedy” and praised the teenager who tried to stop the fight.
“A young man with his whole life ahead of him has been fatally attacked and his family are absolutely devastated,” he said.
“We are doing everything we can to find those involved.
“What we know so far is that a fight broke out between males at the location and as a result this young man received fatal injuries.
“A second independent male, bravely tried to intervene to break up the fight and as a result was also stabbed.”
Hillingdon Council said it was “offering support and counselling” to any of its employees affected.
It is the second murder investigation to be launched in Hillingdon this year – after Tashan Daniel was stabbed to death at Hillingdon Tube Station on 24 September.
Mr Daniel’s family plans to organise a march in central London on 7 December to raise awareness of the impact of knife crime.