My sister acquired Guardian of our Disable sibling 7 ys back in 2015..she moved to California in 2016 and left my sibling here in Arkansas with me

My sister acquired Guardian of our Disable sibling 7 ys back in 2015..she moved to California in 2016 and left my sibling here in Arkansas with me..she was having mental issues and applied for her Disability and got endorsed at some point last yr..she sent me an authenticated letter expressing she could nolonger care for him,which I'm the one that is bn dealing with him. She sent my most seasoned sister that is mental 2-1-22 with a cop to eliminate my sibling from my care.I dread for his wellbeing while he's there. Would I be able to document a request for security?