Teen student Christie Marceau tried to escape an attack at her Auckland home by running outside - but seconds later she was dead.
And her distraught mother and grandmother were at the house, according to a source.
Police responding to an urgent 111 call found Christie's body at her home on Auckland's North Shore at 7.15am on Monday.
They also found a bloodstained knife.
Akshay Anand Chand, who turns 19 tomorrow, was also at the property and was later arrested and charged with killing Christie.