Hi, How do I transfer a mortgaged property from a family member''s LLC to my own LLC?

My mother and brother equally own an LLC in Anchorage, AK. The LLC owns three mortgaged buildings. My mother wants to leave the LLC (and retire). We want transfer one of the mortgaged buildings from the LLC to my own LLC (in WA) with a new (or assumed) mortgage under my name, while my brother retains the two remaining mortgaged buildings under his own LLC. She doesn''t want to take any profits from the transfer of the mortgaged building to me as well - she wants to gift me the equity. Any advice to get this done in a simple way would be appreciated. Josh