New York police shot and killed a hatchet-wielding man on Thursday after he suddenly attacked a group of officers without warning in broad daylight on a busy commercial district in Queens. Police Commissioner William Bratton said police were still trying to confirm the assailant's identity and motive, adding that the officer with the most severe injuries was in a critical but stable condition after suffering a head wound. Security videotape and witness accounts appeared to leave no doubt that the man purposely targeted four rookie New York Police Department officers, police said. Moments before the attack, he was seen on a street corner crouching down to pull the hatchet out of backpack before he charged the officers and began swinging the hatchet with a two-handed grip, police said. Asked if the attack could be related to terrorism, Bratton did not rule it out. He cited the fatal shooting of a soldier in Canada earlier this week - what officials there have called a terror attack - as reason for concern. "This early on, we really cannot say yes or no to that question," Bratton said. The attack occurred at about 2pm while the officers were on foot patrol, police said. Without a word, the man swung at an officer who blocked the blow with his arm. Another officer was hit in the back of the head and fell to the ground. As the man raised the hatchet again, the two uninjured officers drew their weapons and fired several rounds, police said. The bullets killed the assailant and wounded a female bystander, police said. The woman hit by a stray bullet was in hospital with a back wound.