Prosecutors say a New Jersey woman beat her mother and grandmother to death in their beach home.Heather Barbera was taken into custody in New York City last Wednesday on charges of robbery, murder and possession of a weapon by an unlawful person. Investigators say the 41-year-old used a nightstick to beat her mother, 67-year-old Michelle Gordon, and her grandmother, 87-year-old Elaine Rosen, to death.The women were found about 10:30 a.m. July 8 by another relative who had gone to check on them after not being able to reach them by phone.Autopsies determined the women had died of blunt force trauma. Investigators did not say what had been taken during the robbery.According to the Philadelphia Inquirer, Barbera told police she killed the women, took cash and credit cards from them, and went to Atlantic City, then New York City. According to the New York Post, police picked up Barbera's trail when she used her mother's credit card at the Salisbury Hotel on West 57th Street.Surveillance video showed her leaving the women's beach home on July 7. Richard Rosen, Barbera’s uncle, discovered Michelle Gordon and Elaine Rosen dead. He said he had warned the women not to let his niece live with them. He said Heather Barbera had emotional problems and may have been addicted to pills. “It’s unimaginable,” he said. “It was horrible. They were both on the floor. There was blood all over. I was hoping they were alive, even though they were dead.”