A Manassas man was murdered by a heroin overdose, his body dumped in a District of Columbia parking lot and now three people have been charged in the crime, Prince William County police said Tuesday. District police said Gregory Thorton’s body was found in the rear of 300 P St. SW, on Aug. 26 and they’re still awaiting a final ruling from the medical examiner on what killed the 41-year-old. But, court records said, a witness met with Prince William police on Friday and told them Thorton was murdered on Aug. 26 when three people intentionally overdosed him with an intravenous shot of heroin. Prince William police spokeswoman Erika Hernandez said the motive for killing Thorton remains unclear. Monday evening, neighbors on the 10700 block of Primrose Court, near the home where police say Thorton was killed, said they watched as a SWAT team surrounded the house and Vita Russotto, 43, Datagnan Simmons, 37, and Shane Westfall, 25, were brought out in handcuffs. The house is less than a half-mile from Thorton’s home on the 10800 block of Buttercup Circle. According to court records, Simmons told police he was present when Thorton was killed and police said he and Russotto planned Thorton’s deadly heroin overdose. Westfall only has been charged with helping to move Thorton’s body from the house to the sport utility vehicle that carried the dead man to the District. Russotto, who neighbors said bought the house in the lower-middle-class neighborhood several years ago and moved in with her cat, was known for throwing loud parties and people were often coming in and out of the house. “We had our suspicions it was a drug house; this confirms them,” said a neighbor who did not want to be identified, fearing reprisal. The arrests were made after police searched the house Monday, Hernandez said. Examiner Staff Writers Scott McCabe and David Sherfinski contributed to this report.