fbi is offering a $ 20,000 reward for information about bhadreshkumar chetanbhai patel 's whereabouts .
he allegedly killed his wife , palak bhadreskumar patel , on april 12 in hanover , maryland .
taxi driver told investigators she drove him to a hotel in newark , new jersey .
patel was last seen in surveillance footage at a best western near newark liberty international airport on april 13 .
police believe that he is still in the u.s. and is considered to be dangerous .