Investigative Assistance for Violent Crimes Act of 2012 - Authorizes the Attorney General (AG), at the request of an appropriate law enforcement official of a state or political subdivision, to assist in the investigation of violent acts and shootings occurring in a place of public use, and in the investigation of mass killings and attempted mass killings.
Defines "mass killings" as three or more killings in a single incident.
Authorizes the AG to pay rewards of up to $3 million (currently, $2 million), subject to exceptions, for assistance to the Department of Justice (DOJ).
Amends the Homeland Security Act of 2002 to permit the Secretary of Homeland Security (DHS), at the request of an appropriate law enforcement official of a state or political subdivision and through deployment of the Secret Service or U.S. Immigration and Customs Enforcement (ICE), to assist in the investigation of violent acts and shootings occurring in a place of public use, and in the investigation of mass killings and attempted mass killings.
Requires that any assistance provided under this Act be presumed to be within the scope of federal office or employment.