The man suspected of killing eight people in New York City appeared to have planned the attack for several weeks, police say.
NYPD deputy commissioner of counterterrorism John Miller said the truck rampage was "carried out in the name of ISIS (Islamic State)".
He added that as well as being found with two imitation firearms and "multiple knives", suspect Sayfullo Habibullaevic Saipovleft handwritten notes at the scene which said "Islamic State will endure forever".
Saipov has never before been the subject of an NYPD or FBI investigation but "has some connectivity" with subjects under investigation, Mr Miller said.
Of the 12 injured in New York City's worst terror attack since 9/11, one was forced to undergo a bilateral amputation and three others were also critically hurt.
Five of those who died were part of a group from Argentina celebrating the 30th anniversary of their high school graduation.