There is still the will and capacity for killing on streets of Northern Ireland
The sight of masked dissident republicans patrolling the streets of Ardoyne with rifles and a rocket-propelled grenade launcher will send a shiver down the spines of many in Northern Ireland.
It shows beyond doubt that, regardless of the Provisional IRA's ceasefire, there are other republican paramilitaries out there with the will and capacity to kill in pursuit of their goals.
It was in Provisional hands that we first saw RPG-7s in Northern Ireland. The Soviet-made weapon was supplied to republicans in the early 1970s and 80s by Libyan dictator Colonel Gaddafi.
The footage of dissidents, apparently armed with a similar weapon, is an uncomfortable reminder to their old comrades of the unbroken link to the campaign that most in Sinn Fein would today prefer to forget.
The mobile phone footage circulating on social media is not dated, but it is reported to have been filmed recently.
The images are too blurry to identify whether this is an old-style RPG from a Provisional IRA arms dump or a more recent one.
The video should also carry a heavy health warning as it is impossible to verify whether or not the weapons are genuine.
But even if they are authentic, there is no reason to believe that this represents a new and more dangerous threat from anti-Good Friday Agreement republicans.
Various dissident groups have possessed rocket launchers for at least 15 years, but have not inflicted casualties on the security forces with them.
In February 2002, four men were arrested in a field in Coalisland, Co Tyrone, and an RPG-22 recovered in an operation by undercover British soldiers and police. Those charged were later acquitted. The weapon was allegedly linked to the Real IRA.
In August 2008, the Continuity IRA attempted to fire an RPG at a PSNI foot patrol in Lisnaskea, Co Fermanagh. The grenade failed to detonate. The warhead contained Semtex.
Police believed the rocket launcher had been part of the Provisional IRA's arsenal, but had malfunctioned because it hadn't been stored in good conditions.
Despite their fearsome reputation, RPGs would be of limited use to dissident republicans. In the latter stages of their campaign, the Provisional IRA favoured homemade, disposable rocket launchers. They were shorter, lighter, and more adaptable.
Military rocket launchers can travel a longer distance and hit harder, but have many drawbacks. They are harder to use and store, and are generally limited to use against stationary targets.
Homemade rocket launchers - despite their amateurish appearance - are far more versatile and suitable for use in urban areas against mobile targets.
In November 2014, the New IRA released a photograph of one of its members posing with a homemade rocket launcher that was used in an attack against the PSNI.
The grenade, fired from the 'drop and go' launcher, pierced the outer skin of a police Land Rover, but failed to completely detonate, saving the lives of those inside.
That attack - and the fact that dissidents had honed their engineering skills - will have worried the intelligence services considerably more than this footage.
And the fact remains that, despite whatever weapons they may possess, dissident republicans have proved incapable of mounting one 'successful' operation against a military target in recent years. While it remains propaganda photographs and videos that the PSNI is responding to - rather than attacks resulting in fatalities - the security services won't be overly concerned.