On April 21, 2011, Karissa disappeared from Turlock, California. She had been staying with friends and left their home between 2:00 and 3:00 a.m., stating she would return later in the morning. Authorities believe she left on her own.

Karissa had no previous history of running away and maintained a good relationship with her family at the time. She has a pierced septum, a pierced navel, pierced ears, and a pierced cheek. When Karissa was last seen, her hair was dyed a burgundy red color. Her nickname is Rissa.