In an effort to combat lone wolf terrorist attacks, police in the U.S. and abroad are encouraging the public to report unusual changes in a person's behavior that might be a clue to potential trouble, officials said Thursday.

At a conference hosted by the NYPD, about 100 police officials from the U.S., Canada and the United Kingdom explored different ways to stop the spate of lone wolf attacks, such the recent hatchet assault against police officer Kenneth Healey.

NYPD Commissioner William Bratton, speaking to reporters later, said the information on the computer belonging to the man charged with the assault, Zale Thompson, 32, showed he was becoming increasingly volatile in the weeks before the attack on a Queens sidewalk last month. Thompson was shot dead by other officers.

Healey, 25, of Oceanside, has been in a New Hyde Park rehabilitation facility where he has been recovering from a skull fracture. A second officer was less seriously injured.

"Quite clearly, getting access to his computers we were able to see a significant change in focus from the several weeks leading up to the attack," said Bratton of Thompson.

Bratton said the Operation Sentry Conference at One Police Plaza dealt largely with the lone wolf phenomenon because it has become more of a concern than even the threat of a radiological or crude nuclear attack.

Lone actors are being fired up by sophisticated social media postings of terror groups such as the Islamic State and al-Qaida, Bratton noted.

Changes in behavior, along with dramatic changes in appearance, or even subtle ones, can be an indication that something is amiss with a person, added Bratton. It is up to police to develop good relations with communities so there is enough trust for the public to tip off cops about such changes, he said.

Sir Bernard Hogan-Howe, superintendent of the Metropolitan London Police, said that while people are called "lone wolves, they usually know someone, someone who either loves them or cares for them, and those people notice that kind of change in behavior."

Police in the United Kingdom are trying to encourage people to report such behavioral changes if they appear troubling, Hogan-Howe said.