New York Police Department strengthens security for Sunday's marathon

A senior official from the New York Police Department said that enhanced security measures for Sunday's marathon will include snipers, truck barricades filled with sand, and anti-terrorism agents.

Department Chief Carlos Gomez promises that the marathon will be "a very safe event".

Gomez said on Wednesday that there will also be numerous undercover police officers, explosive detection dogs, and helicopters.

Vice Commissioner John Miller said that the attacker had planned it for weeks and did it "in the name of ISIS".