A 17-year-old Massachusetts teenager, Arjun Aravind, was arrested after allegedly murdering his mother, Sudha, 45, and younger brother Siddharth, 14, whose bodies were found with "obvious trauma" in their $1 million Acton home. Middlesex District Attorney Marian Ryan called it "an unspeakable tragedy" and "an incredibly dark day," revealing that days before the killings, the teen exhibited "concerning behavior" online, using ChatGPT to create "fantasy stories" and "Gothic novels" about "the killing of his family" and threats to "his family not surviving." Arjun was charged with two counts of murder, two counts each of assault and battery on a family or household member and assault and battery, plus charges of using a vehicle without authority and motor vehicle theft. The father called police Tuesday for a welfare check after a tutor couldn't get inside and communications went unanswered. Police arrived after 6:30 PM, finding Siddharth dead on the first floor and his mother dead in the basement. The manner of deaths is unconfirmed, pending the chief medical examiner's findings. Arjun had fled in his mother's 2014 Honda Accord and was found early Wednesday morning, 12 miles from the home. The killings occurred Tuesday; Sudha was last seen when her husband left for work around 7AM, and Siddharth was last seen at a recreation facility before noon.