HOUSTON (KTRK) -- The family of the man who is accused of murdering his grandmother said they had recently become more and more concerned about his agitated behavior.Hazel Billingsley, 67, was gunned down early Sunday morning at the home she shared with her grandson, Nathan Billingsley, on East Longwood Meadows near Cypress.Detectives found her body wrapped in a blanket and stuffed in a metal shed in her backyard."She was my rock and one of my best friends", said daughter Carrie Zamir.She hopes her mother is remembered for her caring heart and unending generosity."She did not deserve this. This was so unfair," said Zamir.Her family said Hazel was an avid artist, who captured special moments with both a camera and a paint brush."She saw beauty in everything," said daughter Melanie Billingsley.Nathan Billingsley is charged with his grandmother's murder. Court documents reveal he told investigators the shooting was an accident, but his own brother said there's reason to question that."She told me not to say anything. She said you can't say anything--you can't," said Tanner Hurt.Hurt told Eyewitness News a girl who was staying with Nathan and his grandmother at the home, told him less than a day before the shooting that Nathan was allegedly planning to do something awful."She texted him that he wanted to kill my mom and my grandma and she said that she didn't want to see anybody hurt," said Hurt.He shared that information with his family. They said Nathan had a history of drug abuse, and at times, would make threats. They said he'd been in and out of rehab, and they fear he was using again.They were working on how to handle things, and if or when they should contact authorities, Hurt told ABC13.Now, Nathan's mother says she struggles with guilt about not doing more to stop him sooner."I love him, but I am also angry. And I cannot believe that he could look her -- if he did -- in the eyes and do something cold blooded like this," said Melanie Billingsley.Investigators have not charged anyone else in this case. Billingsley is in custody at the Harris County Jail.