Floral tributes to the victims of the previous week’s attack are placed outside London’s Palace of Westminster on March 27. (Matt Dunham/AP)

British police said Monday that they have found no evidence that London attacker Khalid Masood was linked to the Islamic State, despite a claim by the militant group that he was its “soldier.”

The 52-year-old “clearly had an interest in jihad,” Neil Basu, deputy assistant commissioner of London’s Metropolitan Police, told the BBC. But, Basu said, there was “no evidence or information” that he discussed with others his plans to carry out the attack Wednesday outside Parliament.

Four people were killed and dozens were wounded when Masood drove a rental car through a throng of civilians on Westminster Bridge and then assaulted a police officer with a knife at the gates of Parliament. Masood’s vehicle hit speeds of 76 mph as he drove along the bridge’s sidewalk, and the entire incident lasted just 82 seconds.

Masood was shot dead by security forces after he fatally stabbed the officer, Keith Palmer.

The Islamic State claimed Masood as one of its own the next day in a statement to Amaq, a news agency affiliated with the group.

Basu said investigators have found no evidence to substantiate that claim but acknowledged that the group had influenced Masood.

“His methods appear to be based on low-sophistication, low-tech, low-cost techniques copied from other attacks and echo the rhetoric of [Islamic State] leaders in terms of methodology,” he said.

Police said Saturday that they believe Masood had acted without assistance from others and that his motives may never be fully known. Nine people arrested in the case have been released without charge, while two remain in custody.

Masood was using the online messaging service WhatsApp just minutes before he began his rampage. British officials have in recent days stepped up demands that technology companies enable intelligence services to access encrypted messages, with Home Secretary Amber Rudd saying there must be “no place for terrorists to hide.”

Basu on Monday dismissed as “speculation” reports that Masood had been radicalized while in prison. Masood had a track record of criminal convictions for assault and gun possession but was not on any lists of known extremists. The Saudi Embassy said over the weekend that he had made three visits to the kingdom, where he worked as an English teacher.

“I know when, where and how Masood committed his atrocities, but now I need to know why,” Basu said. “Most importantly, so do the victims and families.”

His comments came as Masood’s mother spoke out for the first time since the killings, saying in a statement that she was “shocked, saddened and numbed” by her son’s actions.

“I wish to make it absolutely clear, so there can be no doubt, I do not condone his actions nor support the beliefs he held that led to him committing this atrocity,” said Janet Ajao, who lives in Wales.

The family of one of the victims also spoke out Monday. Relatives of American tourist Kurt Cochran, who was 54, said they bore no ill will toward anyone after Cochran was killed while walking along the bridge with his wife, Melissa. She suffered a broken leg and rib.

The couple were on the final day of a European vacation to celebrate their 25th wedding anniversary.

“His whole life was an example of focusing on the positive,” said Melissa Cochran’s brother, Clint Payne. “Not pretending that negative things don’t exist, but not living our life in the negative — that’s what we choose to do.”