One of the letters was addressed to the biology department chairman, Gopi K. Podila, but in a subsequent meeting with the students Podila dismissed their complaints, student Caitlin Phillips told the Associated Press. Podila was the first person shot when Bishop allegedly began her shooting spree last Friday.
In at least three complaints to administrators, the students said Bishop had unsettling ways, never looked students in the eye, and frequently talked about her alma mater, Harvard University.
"We could tell something was off, that she was not like other teachers," Phillips told the AP.
ABC News' Susan Donaldson James contributed to this report.