In light of this attack , and a similar attack on French police that occurred earlier on the same day , officers of the New York City Police Department were instructed to " exercise heightened vigilance " and take " proactive measures " . A SWAT unit and two units assigned to the Philadelphia Police Department 's counter-terrorism unit were added to the police patrols in recent days
a similar attack on French police
January 2016 Paris police station attack
Shooting of Jesse Hartnett