Kemper began by carefully destroying evidence. But in the case of Alice (Liu) and Rosalind (Thorpe), he kept their personal possessions in an attempt to get to know his victims.
Rosalind Thorpe and Alice Liu’s student ID cards

Despite media pressure and the formation of a multi-jurisdictional investigative unit (the crimes were committed in four different counties), Kemper kept precious “trophies”, Rosalind Thorpe and Alice Liu’s bags. Every day, he examined the various objects and fantasized about the young women. Around mid-April [1973], he decided to get rid of all the papers or objects he had, including some of Cindy Schall’s objects, as well as the weapon he used to kill the three young girls. He threw it all into the sea.

Rosalind Thorpe’s blood-soaked bra. Kemper shot the 23-year-old student in the side of the head and later decapitated her outside his mother’s apartment.

Source: L’Ogre de Santa Cruz, by Stéphane Bourgoin