According to a report from NBC News, police believe that a hatchet attack on a group of NYPD officers was “a terrorist attack.”

Zale Thompson, a 32 year old from Queens, attacked a group of NYPD officers with a hatchet Thursday, critically injuring one and wounding another. Thompson was fatally shot by the other officers.

“We at this time believe that he acted alone,” NYC Police Commissioner Bill Bratton said Friday in a statement obtained by NBC New York. “We would describe him as self-radicalized. We would describe him as self-directed in his activities.”

At a press briefing, NYC Deputy Police Commissioner John Miller said that Thompson had visited websites with information about ISIS and al Qaeda. He also, according to Miller, viewed videos of violent acts committed by terrorists, including beheadings.

“It appears that this is something that he has been thinking about for some time and thinking about with more intensity over recent days,” Miller told reporters, according to NBC News.

One of Zale’s Facebook friends, however, told The New York Daily News that Thompson was upset about police brutality and had been involved in protesting the death of Eric Garner via chokehold.