Patna, Dec. 16: Bihar police today arrested four persons and said Papiya Ghosh, who taught history at Patna University, was murdered for resisting a robbery — a claim that her friends are finding hard to accept.

Ghosh and her help, Malathi, were stabbed to death on the morning of December 2 in the professor’s sprawling bungalow in Patna’s upscale Pataliputra Colony.

The youths arrested are Shankar Sau, 22, a part-time driver with a Don Bosco schoolteacher; A.K. Roy, 19, an unemployed youth; A.K. Urao, 19, and Manohar Kumar Thakur.