(NewsNation) — Police arrested and charged a 19-year-old man accused of using a machete to attack a group of New York City police officers outside a New Year’s celebration in Times Square, the department announced Monday.

Trevor Bickford, of Maine, is charged with two counts each of attempted murder of a police officer and attempted assault, according to NYPD.

Investigators are reviewing Bickford’s online postings, which included some mentions of Islamic extremist views, an official told The Associated Press. The official could not publicly discuss details about the ongoing investigation and spoke to The AP on condition of anonymity.

Bickford’s statements and diary show he converted to Islam several months ago and was self-radicalized, a source in law enforcement told NewsNation.

Investigators are still looking into a possible motive for the attack.

The attack happened shortly after 10 p.m. about eight blocks from Times Square, according to NewsNation affiliate PIX11. Bickford was just outside the high-security zone where weapons screening took place.

“(The officers) were doing their jobs,” Mayor Eric Adams said. “The jobs that members of the New York City Police Department and other members of police and law enforcement do every day.”

Two of the officers were struck before police shot the man in the shoulder, PIX11 reported.

Both officers were taken to the hospital — one with a fractured skull and the other with a cut, PIX11 reported.

Bickford also was taken to the hospital to be treated for the gunshot wound, The AP reported..

All three are expected to recover, The AP reported.

Investigators have said they believe Bickford traveled to New York City earlier in the week. Local and federal officials had not determined a motive as of early Monday afternoon, according to PIX11.

The kind of attack Bickford is accused of is a prime focus of the FBI — low-tech and conducted alone, but still with the potential to be deadly.

Lone actors present a particular challenge. The same is true of ethnically and racially motivated domestic violent extremists and homegrown violent extremists, who may be inspired by foreign terrorist groups but act alone and without the direct support of any foreign group.

One of the most lethal attacks fitting those parameters was the 2019 shooting at a Walmart in El Paso, in a racist domestic terrorist was accused of killing 23 people.

During a separate October 2017 attack, a legal permanent resident from Uzbekistan killed eight people and injured 11 by plowing a pickup truck through a crowd on a bike path along the Hudson River.

The driver claimed allegiance to Isis.

In New York, police have not disclosed if the suspect in the weekend’s attack near Times Square had any affiliations with a particular group.

In his testimony before Congress in August, FBI Director Christopher Wray outlined several pressing threats.

“The greatest threat we face here in the homeland is from what are largely lone actors already here, largely radicalized online who use easily obtainable weapons to attack soft targets,” Wray said at the time.

The FBI assesses homegrown extremists as the most urgent international terrorism threat.

They remain concerned to a much lesser degree about groups such as Isis and Al Qaeda and their intent to carry out or inspire large-scale attacks on U.S. soil.