Extremist material on sites such as YouTube played a role in radicalising the London Bridge attackers, it has emerged.
A more in-depth profile of the perpetrators has continued to build up as arrests mounted after the weekend's atrocity.
Relatives of 27-year-old Khuram Butt said he drew inspiration from extremist videos on YouTube and wanted to fight in Syria but had his passport taken away by family.
Fahad Khan, 36, the cousin of Butt's wife Zahrah Rehman, claimed his younger relative watched the hateful tirades of preachers online and supported the Islamic State terror group.
He said: "Khuram, I know he was inspired by one of the sheikhs who was giving lectures on YouTube, and he belonged to one specific sector of Islam which had very rigid and strict views.
"Videos about fighting non-Muslims for no reasons, innocent non-Muslims.
"He wanted to go to Syria, yes. I heard from (an) uncle that he wanted to go to Syria to fight, but because of the family pressure, or it might be the intervention by the authorities who seized his passport or whatever, he couldn't go there."
The internet was also described as a catalyst in the radicalisation of Butt's co-conspirator Youssef Zaghba, 21, whose mother claimed: "He had the internet and from there he got everything."
Along with Rachid Redouane, 30, the men died in a hail of police gunfire after spending eight minutes laying waste to the nightlife of south London.
Meanwhile the British Transport Police officer in hospital after being stabbed in the eye has apologised for not doing more to help victims.
The officer, who has not been named, said in a statement: "I feel like I did what any other person would have done. I want to say sorry to the families that lost their loved ones. I'm so sorry I couldn't do more and I want you to know I did everything I could."
Elsewhere, the family of off-duty Metropolitan Police Constable Charlie Guenigault said they were "extremely proud" of his "immense bravery" in facing down the killers on Saturday night.
They said: "Given the opportunity again, Charlie would no doubt do exactly the same if faced with the same situation; helping a fellow police officer in need and protecting the public."
Ilford has become the focus of the inquiry after it emerged that Butt and Zaghba had links to the area.
As intelligence services continued to piece together how the group planned and executed the attack without detection, a host of suspects remained in custody.
Officers have made a number of arrests in a series of raids across east London, mainly in Barking and Ilford.
Twelve people held earlier in the investigation were all released without charge earlier this week.
All eight people killed in the massacre have been identified. There were three Frenchmen, two Australian women, one Canadian woman, one Spanish man and one British man.