(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

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