MUMBAI (Agencies) - An Indian teenager who dared to write a love letter to a sweetheart from a higher caste was beaten and paraded through the streets of his village before being thrown under a train. Manish Kumar, 15, a member of India's Dalit (untouchable) community, a group condemned to carry out the country's very worst jobs, was seized as he made his way to school. The boy was beaten and his hair shaved before he was thrown onto the tracks as his mother begged for mercy. He died from injuries. Witnesses have alleged that the police looked on while the assault took place. One teenager has been arrested and a policeman suspended. Five other men are being detained. The victim's mother, Lalit Devi, told police she had watched "helplessly" as the wheels of the train passed over her son. "The accused killed the boy for writing a love letter to a girl of the same village. There was a scuffle, and he was pushed in front of a train," Superintendent Rajesh Kumar told The Times. Supt Kumar heads the police in Kaimur, the district of the impoverished northern state of Bihar where the attack took place. Love across caste lines is often violently opposed, especially in rural northern India, and it is not uncommon for outraged families to kill to "save the family honour".