The official classification by the UK's Metropolitan Police was made several hours after authorities responded to the scene.
"Senior National Coordinator for Counter Terrorism Policing, Deputy Assistant Commissioner Dean Haydon formally declared the incident as terrorism. The early investigation has revealed a potential motivation linked to Islamist extremism."
In light of today's developments, Priti Patel has ordered a review of security arrangements for all MPs currently serving in parliament. "That he was killed while going about his constituency duties is heartbreaking beyond words. It represents a senseless attack on democracy itself," Patel said.
Sir David Amess, a Tory MP for Southend West, died at the scene of a meeting of constituents at Leigh-on-Sea. As reported earlier today, a 25-year-old man walked in and stabbed the Conservative MP during this event. One that was said to be held on the first and third Fridays of the month.
The Guardian pointed out that the last time a British MP was assassinated in office was Jo Cox in 2016. The paper said that Amess "is one of six British MPs to be killed in office since the second world war."
Additional details from the police missive are that authorities are searching two locations in the London area believed to be linked to the suspect. The investigation is helmed by Met’s Counter Terrorism branch.
While police have not talked much about the background of the suspect, The Independent says it’s a British national of Somali origin.