Israel Police arrested five men overnight Monday on suspicion of aiding and abating two gunmen who carried out a deadly terror attack in Hadera hours earlier, the force said on Monday.
Three of the suspects were residents of the Arab city of Umm al-Fahm, which was also home to the two terrorists, and another was a brother of one of the attackers.
Police said they were investigating whether any of the suspects were members of the same Islamic State-inspired terror cell.
The two men identified as the terrorists were cousins, Ibrahim and Ayman Agbarriya. One of them was convicted of attempting to join the Islamic State (IS) in 2016.
Security forces conducted searches in Umm al-Fahm overnight, and Police Commissioner Kobi Shabtai and Public Security Minister Omer Barlev were also present at the scene.
Relatives of the terrorists, who were shot dead on Sunday by forces who were in the vicinity, said they had no prior indication that the attack was being planned.
Ayman's father Ahmed said his son had spent most of his time at work or in his room.
"We did not feel anything about plans to go to Hadera and start shooting," he said.
I was broadcasting a local soccer match when I was called and told about what had happened. We are in shock," he said.
Late on Sunday, family members and friends arrived to pay their condolences to the families of the terrorists. Some condemned the attack while others said they were pleased with "the message sent to this racist government, for its treatment of the Bedouins in the Negev, the demolition of homes in the Arab sector and the events in the East Jerusalem neighborhood of Sheikh Jarah."
Initial findings of the investigation into the deadly attack showed the two terrorists arrived at the scene and fired shots at Border Police officers who were standing at a bus stop.
They killed Yazen Falah and Shirel Abukarat, both 19, and seriously injured another woman. They continued their indiscriminate shooting, including towards a bike rider who happened on the scene.
Undercover Border Police forces who were dining at a nearby restaurant heard the gunfire and responded quickly, killing the terrorists. Two of them were mildly wounded in the exchange of fire.
The Islamic State claimed responsibility for the attack on their Telegram page.
The gunmen wore IS-inspired garb and other Islamist characteristics including white skullcaps and long beards and carried daggers attached to their belts. One of the attackers had a skull logo on his clothes used by the popular comic book character The Punisher, which was widely appropriated by white supremacists and the far-right in recent years.
This was the second attack carried out by Arab Israeli nationals affiliated with the murderous Islamist group in less than a week.
Last Tuesday, a Bedouin resident of the Negev stabbed four people to death in a killing spree in Be'er Sheva.