Read: DHS Secretary Kirstjen Nielsen's letter on acting deputy secretary's resignation

(CNN)The acting deputy secretary of Homeland Security is leaving the department, the latest top-ranking DHS official to exit.

Claire Grady's imminent resignation, announced Tuesday night by outgoing Secretary Kirstjen Nielsen, paves the way for President Donald Trump's pick of Kevin McAleenan to lead DHS in an acting capacity. Following Nielsen's forced resignation Sunday night, Grady was statutorily next in line to become acting secretary.
Details of Nielsen's letter to employees are below:
Message from Secretary Kirstjen M. Nielsen on Acting Deputy Secretary Claire Grady
    Today, Claire M. Grady, Acting Deputy Secretary offered the President her resignation effective tomorrow. For the last two years, Claire has served this Department with excellence and distinction. She has been an invaluable asset to DHS -- a steady force and a knowledgeable voice.
    In addition to serving as the Department's Deputy for the last year, she served as the Under Secretary for Management overseeing all aspects of the Department's management programs, including financial, human capital, information technology, procurement, physical security and asset management. Claire has led the men and women of DHS who support our operational personnel by providing the overarching business management structure for the Department, while eliminating redundancies and reducing costs. Her sound leadership and effective oversight have impacted every DHS office and employee and made us stronger as a Department.
    Clair has led a remarkable career in public service -- 28 years at the Departments of Homeland Security and Defense -- that is coming to a close. I am thankful for Claire's expertise, dedication and friendship and am filled with gratitude for her exemplary service to DHS and to our country. I wish her all the best in her future endeavors.
    Warmest regards,
      Kirstjen M. Nielsen
      Secretary of Homeland Security