Gurugram, Aug. 16 -- A 29-year-old man was arrested on Thursday for allegedly killing his girlfriend's four-year-old son over suspicion that she had met her husband, police said on Friday. According to police, the accused is Neeraj Kumar, a resident of Sanjay Enclave in Faridabad and a building material supplier. Kumar's 32-year-old girlfriend was separated from her husband and has three daughters and a son. While the daughters live with the husband, the woman and her son have been living with Kumar for a year. Police said she had left the house with her son three days ago after a fight with Kumar and returned on Wednesday night. On coming back, when she asked Kumar for money to pay the auto rickshaw driver, he started beating her. Yashpal Yadav, public relations officer of Faridabad police, said Kumar suspected that she might have met her husband or some other male friend. "Enraged, he took away the woman's son from her arms and took him inside. He sent her away from the house and asked the child where her mother had gone in the past three days," the PRO said. When the boy could not answer anything clearly, Kumar throttled him to death, investigators said, adding that he slept in the same room overnight with the child's body. On Thursday morning, he told the neighbours that the child was unresponsive and that he was unwell last night, to avoid any suspicion. Officials said that the neighbours suspected foul play and alerted the police control room, following which teams reached the spot. Preliminary investigation showed that the boy had injury marks on his neck, suggesting murder. Kumar was questioned, and he confessed to the police that he killed the child in a fit of rage. On the basis of the woman's complaint, a murder case was registered against Kumar at Saran police station on Thursday and the child's body was handed over to his mother after an autopsy....