JOSHUA TREE, Calif. (KABC) -- Kaylee Ledford, 27, is charged with murder after her 3-month-old son died at the hospital in September 2015.For her ex-boyfriend, Justin Mealer, the case is a heartbreaking reminder of what happened four years ago to a son he had with Ledford.That boy, Deacon, was born about two months early and stayed in the hospital for about 30 days, Mealer said. Then he was sent home with a heart monitor that would buzz if he didn't breathe after a certain amount of time.He says Ledford didn't want to use the monitor and they fought about it all the time."Her exact statement to me was I've been a mom since I was 14 years old, I don't need a machine to tell me how to take care of my kids," he recalled.But on July 10, 2012 Deacon stopped breathing. Mealer called 911 and paramedics arrived at their Twentynine Palms home. The baby boy was pronounced dead at the hospital."She's the reason my son is dead," Mealer said. "Whether it was through neglect and just bad judgment, or by intent, my son is dead."Ledford was not arrested in that case because the San Bernardino County Sheriff's Department didn't think there was anything suspicious about the death.Then on Sept. 1, 2015, paramedics were called to Ledford's home again for a different baby boy who wasn't breathing.That boy was also pronounced dead. This time, after the autopsy was complete, Ledford was charged with murder.She was arrested last week at her home on the military base at Twentynine Palms, where she is married to a U.S. Marine.ABC7 asked to speak to Ledford in jail, but she declined.Now the District Attorney's office said regarding Deacon's death in 2012: "With new evidence there's always the potential we could reopen the 2012 case."Ledford's bail in the 2015 case is set at $1 million.