Investigators say Nathan Carman also killed his grandfather in 2013, and after his half-million-dollar inheritance ran out, he targeted his own mother. Subscribe to WCVB on YouTube now for more: http://bit.ly/1e8lAMZ Get more Boston news: http://www.wcvb.com Like us: https://www.facebook.com/wcvb5 Follow us: https://twitter.com/WCVB Instagram: https://www.instagram.com/wcvb5/