The U.S. Department of Justice is pursuing a criminal case in the beheading of journalist James Foley, Attorney General Eric Holder said Thursday.

“The Justice Department is actively pursuing justice in this case,” Holder said in a speech. “We have an open criminal investigation. And those that would perpetrate such acts need to understand something. This Justice Department, this Department of Defense, this nation; we have long memories and our reach is very wide. We will not forget what happened and people will be held accountable, one way or the other.”

Also read: Obama: ‘Entire World Is Appalled’ by James Foley’s Murder

The announcement is likely to raise criticism that the Obama Administration is dealing with acts of terror in courtrooms rather than on the battlefield, a persistent criticism by Republicans. But Holder’s mention of the Department of Defense signaled that the administration is pursuing Foley’s killer’s in both arenas.

The group known as ISIS, or ISIL, claimed responsibility for the videotaped murder, which was briefly posted online this week. ISIS has marauded across Iraq and Syria, trying to create a state based on a hardline version of what it considers Islam. The group has kidnapped and killed untold numbers of civilians while trying to force other Muslims and Christians alike to convert to its version of Islam.

Also read: James Foley Death Exposes Secret Ransoms to Free Captured Journalists

Holder spoke a day after President Obama pledged that when Americans are harmed, “we do what’s necessary to see that justice is done.”

Obama also said before the murder, however, that the U.S. would not return thousands of troops to Iraq. Instead, the U.S. is supporting Iraqi government forces and Kurds who are battling ISIS.