DANBURY — A West Street man was arrested Friday after an investigation revealed he sexually abused a 14-year-old girl, police said. After a five-month probe, the Danbury Police Department’s Special Victims Unit was issued an arrest warrant last week for 66-year-old Romulo Medina. The man was taken into custody without incident and charged with first-degree sexual assault and two counts of risk of injury to a minor. Police did not release details on the alleged abuse. Medina was held on a $60,000 bond.