. As the principal Federal official for domestic incident management, the Secretary of Homeland Security coordinates the Federal resources utilized in the prevention of, preparation for, response to, or recovery from terrorist attacks, major disasters, or other emergencies.
Also according to the Federal Emergency Management Agency (FEMA) the Secretary of Homeland Security also does the following:
Provides the President with an overall architecture for domestic incident management and coordinates the Federal response, when required, while relying upon the support of other Federal partners.
Contributes elements of the response consistent with the Department of Homeland Security's (DHS’s) mission, capabilities, and authorities.