President Barack Obama is set to deliver a rare address from the Oval Office Sunday evening on the terror threat facing the United States. Following a mass shooting in San Bernardino, California, that left 14 dead and at least 17 more wounded Wednesday, the president will brief the nation on the danger from Islamic extremism.

The assault on San Bernardino occurred Wednesday morning, when a husband-wife duo stormed the husband’s holiday party at his office, opening gun fire on employees. The pair took off in a rented getaway car and both were killed later that day in a shootout with police.

After the death toll climbed to 14, the massacre became the deadliest terrorist assault on U.S. soil since the 9/11 attacks that killed nearly 3,000 people. Authorities are looking into radicalization as a motive, as the female shooter posted a statement to her Facebook praising the terrorist group known as the Islamic State group, ISIS or Daesh around the time she and her husband were conducting the attacks.

"The investigation so far has developed indications of radicalization by the killers and of potential inspiration by foreign terrorist organizations," said FBI Director James Comey, the Associated Press reported.

In the wake of the revelations concerning the potential terrorist roots of the shooters -- as well as the ongoing aftermath of a series of coordinated assaults Nov. 13 on Paris that left 130 dead -- Obama will address the nation Sunday night. He is expected to lay out his plan for fighting ISIS as well as for combating homegrown radicalization.

"He will reiterate his firm conviction that ISIL will be destroyed and that the United States must draw upon our values – our unwavering commitment to justice, equality and freedom – to prevail over terrorist groups that use violence to advance a destructive ideology," the White House said in a Saturday statement, reported the Hill.

The speech will air live on ABC, CBS, Fox and NBC at 8 p.m. EST. For people without cable subscriptions, the White House will also live-stream the 15-minute speech on their website.