The family of an 18-year-old who died after being stabbed in a "disturbance" at a house has described him as a "bright young man".
Risaan Udayakumar, from Wembley, died in hospital after the incident at an address in The Avenue in Watford just after 21:50 BST on Tuesday.
A 16-year-old boy appeared in court on Thursday, charged with murder, and has been remanded in custody.
Mr Udayakumar's family said his death had left a "gap that cannot be filled".
Mr Udayakumar had just finished his first year studying civil engineering at university.
In a statement, his family said he was a "gentle, academically talented student" and they could "not understand why this has happened to such a bright and caring young man".
Det Insp Justine Jenkins, from the Bedfordshire, Cambridgeshire and Hertfordshire Major Crime Unit, said it was believed the stabbing was an "isolated incident".