BROOKLYN - The death of a man found dismembered inside a Sheepshead Bay apartment has been ruled a homicide by the medical examiner.Police have taken a man into custody in connection with the killing. According to authorities, the remains of the victim, believed to be the suspect's roommate, were found in plastic containers inside a fourth-floor apartment at 3395 Nostrand Ave.Neighbors have described the suspect, whom sources identified as Sergey Mamontov, as a quiet and standoffish man. Detectives say there were ongoing disputes between the two roommates.Police say the crime scene inside the apartment is complicated and that they will be going through every inch of it in search of evidence.