The alleged father and son gunmen who killed at least 15 people in a mass shooting at Australia's Bondi Beach traveled to the Philippines in the weeks leading up to the attack and may have been inspired by the ISIS terrorist organization, Australian Prime Minister Anthony Albanese said.

ISIS gunman kills two Iowa National Guard members in Syria terrorist attack. Community mourns loss of Nate Howard and fellow soldier in tragic incident.

Sgts. William Nathaniel "Nate" Howard and Edgar Torres-Tovar were killed in Syria while they were stationed with the Iowa National Guard.

The shooting happened during a mission by U.S. and Syrian forces in a historic central town near Palmyra on Saturday. President Trump and U.S. military officials attributed the attack to ISIS.

President Donald Trump vows "very serious retaliation" after an ISIS gunman killed two U.S. Army soldiers and an interpreter in a Syrian ambush, leaving three other soldiers wounded.

The attack, which took place in the city of Palmyra, comes a year after the fall of Syrian President Bashar al-Assad and the lifting of U.S. sanctions.

Prime Minister Anthony Albanese said two gunmen who killed 15 people at a Jewish holiday celebration were motivated by the Islamic State.

Investigators found improvised explosive devices (IEDs) and at least two black ISIS flags in a car at the scene registered to Naveed Akram.

CBS News national security contributor Samantha Vinograd breaks down the current state of ISIS following the deadly attack on an Australian Hanukkah celebration.