SYDNEY, Australia — Australian police said the two alleged gunmen behind the deadly attack on a Hanukkah celebration at Sydney’s Bondi Beach had travelled to the Philippines weeks before the assault and appeared to have been inspired by Islamic State ideology.

The shooting on Sunday killed 15 people and injured dozens, marking Australia’s worst mass shooting in nearly three decades. Authorities are treating the incident as a terrorist attack targeting the Jewish community.

Investigators are focusing on two key lines of inquiry. One involves the overseas travel of the suspects, identified as Sajid Akram, 50, and his son Naveed, 25, who reportedly visited the Philippines shortly before the attack. The other concerns two homemade Islamic State flags allegedly found in a car registered to one of the suspects and parked near the scene of the assault.

Philippine authorities said the pair arrived in the country on November 1 and travelled to Davao City on the southern island of Mindanao, a region long affected by Islamist extremism. They returned to Sydney via Manila on November 28, about two weeks before the attack.

Police said it remains unclear what the two men did during their stay in the Philippines. Security analysts have long warned that time spent overseas, particularly in areas with active extremist networks, can play a critical role in radicalisation, even when no formal military training is involved.

While some extremist groups still operate in parts of Mindanao, Islamic State’s presence there has significantly declined in recent years. However, small groups of militants and sympathisers remain active, according to regional security officials.

Authorities said there is no evidence at this stage that the suspects received formal combat training. Investigators noted that the attack itself was not complex, involving gunfire directed at unarmed civilians during a religious gathering. Sajid Akram legally owned firearms and held a gun licence, which may have been sufficient for carrying out the assault.

Counterterrorism experts say overseas travel can also serve as a means of ideological reinforcement, fostering commitment and purpose rather than technical skills. Such radicalisation can occur through isolation, close association with like-minded individuals, or exposure to extremist teachings and propaganda.

In recent years, Islamic State and similar groups have increasingly relied on inspiring individuals to carry out attacks independently, a strategy often described as leaderless jihad. This approach has been linked to several deadly attacks worldwide, including incidents in Europe and the United States.

Police cautioned that many details surrounding the Bondi Beach attack remain under investigation. However, officials said the case underscores that Islamic State’s ideology continues to pose a global security threat, more than a decade after the group’s emergence.