A man is facing first-degree murder charges for allegedly stabbing his brother in the neck in a Thornton parking lot. The victim, identified as 29-year-old Stephen Rivas, died from a stab wound to the neck after being rushed to the hospital. Zamien Rivas was arrested and charged with first-rendering murder. The woman who called 911 reported hearing the two brothers arguing about Stephen's claim to be a Crips gang member. She also saw Zamien throw a knife during the fight, which he reportedly picked up before fleeing the scene.