Investigators are baffled by the fatal shootings last week of a Chinese-American family of four, including two young boys, at their suburban Houston home. Authorities have not yet determined a motive for the killings nor identified any suspects, Harris County Sheriff Adrian Garcia said on Tuesday. All four victims, including the boys aged 7 and 9, were shot in the head. The names of the victims have not been released but local media identified the children as Timothy Xie Sun and his younger brother Titus Xiao Sun, both pupils at Sampson Elementary School. The two boys were last seen at school on January 23, although bad weather closed schools in the district on January 24 and 28. Public records show the home at 14015 Fosters Creek belonged to 49-year-old Mei Xie and her husband Maoye Sun, 50. The couple were married in Harris County in November 2000. Garcia said his office was working with the Chinese consulate to locate relatives. Authorities said the husband and wife were naturalised US citizens who had emigrated from China. They did not say when the family arrived in the United States. Garcia said deputies went to the family's Cypress home last Thursday after the husband's colleagues became concerned when he had not shown up for work for several days. Deputies found the back door open and inside discovered a "horrific crime scene", Garcia said. Harris County Sheriff's Office Sergeant Felipe Rivera said the victims had been found in their bedrooms. He declined to give other details of the crime scene, only saying they had not been tied up and that no weapons were found at the home. Autopsies done by the Harris County Institute of Forensic Sciences have ruled the deaths as homicide. Garcia said authorities did not know the type of weapon used in the killings. Rivera said investigators had found signs of forced entry via a window but that it was unclear if it was recent damage. Investigators did not know if anything was taken from the home. "It is baffling," Rivera said of the case. The father, a mechanical engineer at Cameron, a Houston-based oil and gas industry equipment manufacturer, was last at work on January 24. Cameron spokeswoman Sharon Sloan confirmed that he had worked for the company but declined to comment further.