Hatchet-wielding man has authorities struggling to understand motivation

The attack on four NYPD officers by a man with a hatchet has led some to label it terrorist activity while others have said he could just be an angry man.

The man with a metal hatchet who attacked four New York City Police Department officers Thursday afternoon, wounding one and critically injuring another before he was shot dead, has law enforcement officials split between labeling him a possible terrorist or "just an angry guy," according to multiple media reports.  

The attacker approached a group of NYPD officers at 2 p.m. in the city's borough of Queens. The police were posing for a photograph at the behest of a freelance photographer. The man charged at the officers with his hatchet swinging, a Police Department spokesman said. 

A woman who was standing nearby was struck by a stray bullet in the back. She underwent surgery and is recovering at the hospital, police said. 

It is unknown at this time what the motivations of the attacker, identified as Zale Thompson, were. 

"At this point, no known motive for this attack has been established," Police Commissioner William Bratton said in a press conference. 

Video footage of Mr. Thompson moments before the attack appears to show a man running toward the officers, unprovoked.

Following this week's attack at the Canadian Parliament by Michael Zehaf-Bibeau that left one soldier dead – which officials have called a terror attack – an internal memo was reportedly circulated in the NYPD urging officers to maintain a heightened level of awareness. 

Asked if Thursday's attacks could be linked to terrorism, Bratton indicated it was possible. 

"This early on, we really cannot say yes or no to that question," Bratton said. 

But one police source told ABC News that the attacker may just be a troubled young man who decided to lash out. 

"The initial impression is that he's just an angry guy who's ranting about the American government and American oppression of foreign people," the source told ABC News. 

The NYPD officers were relatively inexperienced, having just graduated from the city Police Academy on July 8. 

In addition to the Canadian parliament assault, a recent string of attacks in the West by individuals claiming affiliation with radical Islam or militant beliefs has stoked concern. A hit-and-run this week that left a Canadian soldier dead was pronounced a terrorist attack by Canadian politicians. And last month, a man who had converted to Islam was shot and wounded after he beheaded a co-worker at a food processing plant in Oklahoma. 

Material from the Associated Press and Reuters was used in this report.