US TV host Savannah Guthrie’s brother, Cameron, has issued a desperate plea to his mother’s potential kidnappers, as the first deadline listed in a reported ransom note expired.Nancy Guthrie, 84, was last on Saturday evening, when she was dropped home by her son-in-law in Pima County, Arizona.In a video posted to social media on Thursday night, US time, Cameron pleaded with possible captors to contact his family.“Whoever is out there holding our mother, we want to hear from you,” said Cameron, the eldest of Nancy’s three children.“We haven’t heard anything directly. We need you to reach out and we need a way to communicate with you so we can move forward. But first, we have to know that you have our mum. We want to talk to you, and we are waiting for contact.”US outlets TMZ and KOLD-TV both received purported ransom notes demanding an unspecified amount of money in exchange for Nancy.FBI Phoenix’s special agent in charge Heith Janke, told reporters earlier on Thursday authorities are investigating a ransom note linked to Nancy which gave an initial deadline of 5pm Thursday and a second deadline of next Monday.However, the letter – which included details about an Apple watch and a flood light – did not include a proof of life or a method for authorities or Nancy’s family to make contact with the senders, said special agent Janke.“In a normal kidnapping case, there would be contact by now, trying to discuss that,” he said, without elaborating further on the contents of the note.The FBI announced up to $50,000 would be awarded to the person who provides information leading to the return of Nancy or an arrest of someone involved in her disappearance.‘Still out there’Pima County Sheriff Chris Nanos told Thursday’s press conference police are continuing efforts to locate the 84-year-old.“Right now, we believe Nancy is still out there,” he said.“We just want her home and find a way to get to the bottom of all of this.”Sheriff Nanos said authorities have not identified any suspects nor a person of interest.“We’re not there yet,” he said. The Sheriff confirmed blood found on the front steps of Nancy’s home tested positive for her DNA.He also revealed the clearest timeline of Nancy’s disappearance, noting she left her house to visit her family’s home at 5.32pm on Saturday to play games and have dinner.Hours later, her garage door opened at 9.48pm and closed two minutes later, with police believing this is when Nancy returned home and went to bed. At 1.47am on Sunday, her doorbell camera disconnected and at 2.12am, software detected a person on the camera, but the sherrin said no video was available.At 2.28am, her pacemaker app disconnected from her phone.2am pacemaker pingNancy’s 2am pacemaker spike on the day she vanished could mean that the elderly woman was involved in a heart rate-surging struggle with her possible captors, a lead cardiologist speculated on Thursday.When investigators reached the home hours after she was reported missing, around noon on Sunday, the devices were still inside the house.“If a person was in a physical struggle, that might have created a rapid heartbeat … the pacemaker would have detected that and potentially reported it,” Dr. Jonathan Reiner, who was former vice president Dick Cheney’s cardiologist, chillingly told CNN.Arizona authorities previously said the 84-year-old’s implanted medical device stopped syncing with her Apple devices, including a watch and her iPhone, around 2am on Sunday, close to the time police believe she was abducted from her Tucson home.“A pacemaker not only has the ability to create a heartbeat, triggering a heart to beat, but it’s also a sophisticated monitor of the patient’s heart rhythm, and a pacemaker is programmed to check in once a day, just to check in with its communication device and then ultimately the app that monitors it once a day,” he explained. “Typically that’s at night, so at 2 o’clock in the morning, that’s all it might have been doing.”Pacemakers cease to sync with the communication devices when they’re between five and 20 feet away from each other, Reiner said – making it “hard to know exactly what that means” as it pertains to Guthrie’s movements early Sunday morning. “But it does tell us that she was in close proximity to her cell phone at 2 o’clock in the morning … until that time, they were together,” he said. The top doc said it would “be easy to know” whether the spike indicated an innocent, routine check-in or an arrhythmia, which would suggest a struggle – and Guthrie’s physician would have the answer. “All that needs to be done is to check with the implanting physician because that’s where the data goes,” Reiner said. Regardless, “an 84-year-old is a very fragile person – even a fairly robust person in their 80s is at risk of a very severe injury if they fall,” he warned.“So, Mrs. Guthrie, if she lost her footing or was pushed to the ground or somehow fell, that could result in a severe injury,” he said, adding that the unidentified medications she takes may also work as a blood-thinner, which would make matters worse. Arizona law enforcement previously said they found drops of blood and signs of a struggle at Guthrie’s home – as well as her lifesaving, daily medication. “The clock is literally ticking,” Pima County Sheriff Chris Nanos said in reference to the meds.Star’s emotional messageSavannah broke her silence on her mother’s disappearance on Wednesday night, US time, sharing an emotional video message to social media that was captioned “bring her home”.Appearing alongside her brother and sister, the visibly tired journalist struggled to hold back tears, saying her mum “is our heart and our home”.“She’s 84-years-old, her health, her heart is fragile. She lives in constant pain. She is without any medicine, she needs it to survive and she needs it not to suffer,” she said.The Today host then addressed reports of ransom letters being sent to media outlets, including one that demanded millions in bitcoin, issuing a direct message to the potential kidnapper.“We’re ready to talk. However, we live in a world where voices and images are easily manipulated. We need to know, without a doubt, that she is alive and that you have her. We want to hear from you, and we are ready to listen,” Savannah said.“Please, reach out to us.”She also directly addressed her mother, stressing “everyone” is looking for her and that they “will not rest” until the family is reunited.