(CNN) -- Philip Chism, the Massachusetts teenager accused of raping and killing his algebra teacher, became visibly upset when the teacher, Colleen Ritzer, spoke about the teen's home state of Tennessee after class, according to a police affidavit unsealed Friday. A ninth grade student told investigators that she was in class with Chism and Ritzer after school on the day of the crime, the affidavit said. She said the teacher and Chism were talking about China but, at some point, Ritzer mentioned the student's home state of Tennessee. Chism became "visibly upset," the student said. When Ritzer noticed that Chism was upset, she changed the subject, said the unidentified student, who described Chism as "talking to himself."
@highlight
Affidavit describes chilling note allegedly left by Massachusetts teen after killing teacher
@highlight
"I hate you all," said handwritten note found next to body of Colleen Ritzer
@highlight
Court papers say Philip Chism was upset after teacher spoke of his home state, Tennessee
Tennessee
Tennessee
Tennessee
Documents filed in a @placeholder court 12 years ago shed light on a troubled relationship.
Colleen Ritzer
Ritzer
Ritzer
Ritzer
Colleen Ritzer
Dressed in pink, hundreds mourn @placeholder, slain Massachusetts teacher
Massachusetts
Massachusetts
Dressed in pink, hundreds mourn Colleen Ritzer, slain @placeholder teacher