Investigators are searching for answers about what caused a house fire that led to the death of a child Friday afternoon on Clarkson Street in Thornton. Nathan Hill was at work when a stranger knocked on the door of his real estate office, telling him there was a fire just next door. "My first thought is, everybody in our office, let's get out, let's move the vehicles, let's be safe," Hill said. "And then, little do I know, there's a child next door that can't get out and loses his life. It's sad." Read more: https://www.9news.com/article/news/local/child-killed-thornton-house-fire/73-c64b332d-056b-4bf4-ab20-574a6f22afb5 ----- More local videos here: https://youtube.com/@9news Subscribe to NEXT: https://youtube.com/@Nexton9NEWS Stay connected: 9NEWS Website: https://www.9news.com/ Facebook: https://www.facebook.com/ilike9news Twitter: https://twitter.com/9NEWS Instagram: https://www.instagram.com/9newsdenver/ Download the 9NEWS App: https://www.9news.com/appredirect/ Sign up for the 9NEWSLETTER: https://www.9news.com/email 9NEWS (KUSA) is located in Denver, Colorado.