Syria blasts signal dangerous escalation of violence
First the facts - the second of two bomb blasts that went off on Thursday morning in the Damascus district of al-Qazzaz constitutes the most destructive explosion yet since the Syrian uprising began last year.
Syrian state TV has been quick to show images of blood-spattered cars riddled with shrapnel or worse. It says at least 55 people have been killed.
It's the fifth time this year that the once peaceful capital has been bombed. Previously the worst carnage took place on 17 March, when at least 27 people were killed and 100 wounded.
A military expert on Improvised Explosive Devices (IEDs), who asked not to be named, told the BBC that the attack was "extremely well-planned and sequenced", designed to inflict maximum casualties on intelligence personnel.
"The attack was also mounted with scant regard to civilian casualties," he said.
"It would appear that the first device was a classic 'come-on' - a relatively small device detonated to encourage personnel to leave their buildings and move into exposed areas - for a subsequent attack with a much larger device.
"This second device probably contained between 225kg and 450kg of explosive and was most likely initiated by remote control at a time to maximise casualties. From the nature of the damage inflicted, it would appear that homemade explosive was used."
The key questions are who did it and why?
The Syrian government has condemned the blasts as the work of terrorists, painting opposition rebels as deliberate violators of the UN-brokered ceasefire. The principal target was the so-called "Palestine Military Branch" where many of the regime's enemies have allegedly been interrogated and tortured.
But the Syrian opposition has denied they were behind the blasts, accusing the regime instead of carrying them out on their own people in order to discredit the opposition and gain sympathy from the UN monitors now in town.
So is it really possible that a sovereign state like Syria could be so cynical as to deliberately kill its own forces for some dark, Machiavellian purpose?
Sajjan Gohel, an expert on transnational terrorism at the Asia Pacific Foundation, thinks so.
He told me: "The Syrian regime is more than capable of planning attacks against its people for propaganda purposes. We have seen that already in Lebanon in the past."
He adds that it is possible the blasts were designed to deflect international criticism of government forces' shelling of civilian areas.
But there is also a "third force", distinct from the mainstream opposition, that has claimed responsibility for major attacks in the past.
The shadowy "al-Nusra Battlefront" emerged in January and has since said it was behind previous car and truck bomb attacks, including the one in March on police HQ and Airforce Intelligence.
The group has a distinctly jihadist agenda - it refers to its fighters as "mujahideen of Sham in the arena of Jihad" and there are suspicions it may have links to al-Qaeda.
Earlier this year, the successor to Osama Bin Laden, the bespectacled al-Qaeda leader, Dr Ayman al-Zawahiri, posted a message online urging Muslims to support the revolution in Syria, but the mainstream opposition said they wanted nothing to do with him or his organisation.
Yet there is a growing belief that only two organisations have the bomb-making expertise and organisation to mount such spectacular, planned and effective attacks in Syria - al-Qaeda in Iraq (which shares a border with Syria) and the Syrian government itself. It all depends on who you believe.