So says the FBI, which has received warnings that a new anarchist militia may take advantage of trick-or-treat to conduct some dirty tricks of their own on local law enforcement agencies. Both NBC and the New York Post have sources telling them that the FBI is taking the threat seriously, which involves the kind of street violence seen in Ferguson and other flashpoints over the use of lethal force by police. The strategy will be to ambush cops as they respond to reports of disturbances:

The officials told NBC News that police forces have been warned that members of an anarchist group called the “National Liberation Militia” might be planning to dress up in costumes, cause a disturbance then ambush responding officers.

There is no specific or credible information about when or where the so-called “Halloween revolt” plot will play out, the officials cautioned.

They told NBC News that the National Liberation Militia was a known group — though offered no other details on the group’s makeup. Little record for such a group could be found online.

ABC’s Detroit affiliate reports that the plot is being driven by a subset of the shadowy group called the Grim Creepers. Despite the silly name, the Detroit police department says the threat is serious:

The Grim Creepers are proposing the Halloween revolt. They’re part of an extremist group known by feds as the National Liberation Militia.

Detroit Police Assistant Chief Steve Dolunt acknowledges the serious nature of the threat. He learned the group has encouraged members to wear Halloween masks and create a disturbance to lure in officers and then to use weapons on them – weapons such as bricks, bottles and firearms.

As a result of the warning, cops in Detroit and throughout southeast Michigan are keeping an eye out for anything out of the ordinary.

They’re also asking parents of trick-or-treaters and anyone else to report suspicious activity.

In one sense, this sounds more like a put-up job to tie up police rather than an organized revolt. On the other hand, we have already seen the rise of anarchic protests and violence over the past year, a trend that had seemed to settle down somewhat over the last few months. It reminds one of the social turmoil of the late 1960s and 1970s, when groups with names like the Symbionese Liberation Army created destruction and death for their radical agenda — and targeted cops, too. It pays to take these threats seriously, in other words.

In response, the FBI and law-enforcement agencies want to emphasize the public’s role in security by stressing the “see something, say something” approach. That’s all well and good, as long as one doesn’t report a suitcase clock that looks suspiciously like a bomb. Can’t wait to hear all about supposed overreaction and bigotry when people actually follow through on that advice.