Police line do not cross
File photo: US police tape Reuters

A 15-year-old suspected of stabbing a woman to death at her family home had a 'death list' that included the victim's younger sister, prosecutors say.

Makayla Grote, who had graduated from Green Mountain High School in just 2016, died in hospital after suffering stab wounds to the head and chest.

Longmont police said they had responded to a call at 6:12pm on Saturday 18 November and located an injured female who was transported to a local hospital where she died. Authorities said a juvenile suspect fled the scene but was arrested in Lakewood on Sunday 19 November around 1am.

Police said the 15-year-old suspect faces a first-degree murder charge.

Court documents seen by CBS Denver alleged that Grote's younger sister had received "troubling text messages" from the teenage suspect and that the sister's name appeared on a supposed 'death list' the suspect kept.

The suspect is alleged to have stopped by Grote's house earlier in the day where she, her sister and mother were inside. The suspect was then reported to have threatened his mother and assaulted his grandfather before returning to Grote's home.

Prosecutors told the court that Grote's sister was in the shower so she was the one who answered the door, 9 News reported. The suspect allegedly stabbed her in the head and chest with a 'hunting knife'.

The teen suspect has not been identified because he is a minor. Police said that they found molotov cocktails at his home along with the 'death list' and a list of tools to carry out the killings, CBS reported.

He had apparently been reported as a runaway and has previously faced charges. He was also a former suspect of Green Mountain High School. The suspect will reportedly appear in court on Wednesday morning, until then he is in custody at a juvenile detention center.