Complex sentence: In February 2015, both girls accused of perpetrating the stabbing were interrogated by local police, in which they said they planned the stabbing because they wanted to keep Slender Man from harming themselves and their families.
Split into simpler sentences: In February 2015, both girls accused of perpetrating the stabbing were interrogated by local police. In their interrogations, the girls said they planned the stabbing because they wanted to keep Slender Man from harming themselves and their families.