Bashar Barhoum woke in his dungeon prison cell in Damascus at dawn Sunday, thinking it would be the last day of his life.

The 63-year-old writer was supposed to have been executed after being imprisoned for seven months.

But he soon realized the men at the door weren't from former Syrian president Bashar al-Assad 's notorious security forces, ready to take him to his death. Instead, they were rebels coming to set him free. 

As the insurgents swept across Syria in just 10 days to bring an end to the Assad family's more than 50-year rule, they broke into prisons and security facilities to free political prisoners and many of the tens of thousands of people who disappeared since the conflict began back in 2011 or even before.

Barhoum was one of the freed who was celebrating in Damascus.

"I haven't seen the sun until today," Barhoum told The Associated Press after walking in disbelief through the streets of Damascus. "Instead of being dead tomorrow, thank God, he gave me a new lease on life."

Barhoum couldn't find his cellphone and belongings in the prison, so he set off to find a way to tell his wife and daughters he's alive and well.

Videos shared widely across social media showed dozens of prisoners running in celebration after the insurgents released them, some barefoot and others wearing little clothing. One of them screams in celebration after he finds out the government has fallen.

Torture, executions and starvation

Syria's prisons have been infamous for their harsh conditions. Torture is systematic, say human rights groups, whistleblowers and former detainees. Secret executions have been reported at more than two dozen facilities run by Syrian intelligence, as well as at other sites. 

In 2013, a Syrian military defector, known as "Caesar," smuggled out over 53,000 photographs that human rights groups say showed clear evidence of rampant torture, but also disease and starvation, in Syria's prison facilities.

Syria's feared security apparatus and prisons did not only serve to isolate Assad's opponents, but also to instill fear among his own people, said Lina Khatib, associate fellow in the Middle East and North Africa program at the London think-tank Chatham House. 

"Anxiety about being thrown in one of Assad's notorious prisons created wide mistrust among Syrians," Khatib said. "Assad nurtured this culture of fear to maintain control and crush political opposition."

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Just north of Damascus in the Saydnaya military prison, known as the "human slaughterhouse," women detainees, some with their children, screamed as men broke the locks off their cell doors. Amnesty International and other groups say that dozens of people were secretly executed every week in Saydnaya, estimating that up to 13,000 Syrians were killed between 2011 and 2016. 

"Don't be afraid … Bashar Assad has fallen! Why are you afraid?" said one of the rebels as he tried to rush streams of women out of their jam-packed tiny cells.

Tens of thousands of detainees have so far been freed, said Rami Abdurrahman of the Syrian Observatory for Human Rights, a Britain-based pro-opposition war monitor.

Over the past 10 days, insurgents freed prisoners in cities including Aleppo, Homs and Hama, as well as Damascus.

Families anxiously wait for loved ones

Omar Alshogre, who was detained for three years and survived relentless torture, watched in awe from his home far from Syria as videos showed dozens of detainees fleeing.

"A hundred democracies in the world had done nothing to help them, and now a few military groups came down and broke open prison after prison," Alshogre, a human rights advocate who now resides in Sweden and the U.S., told The Associated Press.

Meanwhile, families of detainees and the disappeared skipped celebrations of the downfall of the Assad dynasty. Instead, they waited outside prisons and security branch centres, hoping their loved ones would be there.

They had high expectations for the newcomers who will now run the battered country.

"This happiness will not be completed until I can see my son out of prison and know where he is," said Bassam Masri. "I have been searching for him for two hours. He has been detained for 13 years."

Rebels struggled to control the chaos as crowds gathered by the Court of Justice in Damascus.

Heba, who only gave her first name while speaking to the AP, said she was looking for her brother and brother-in-law, who were detained while reporting a stolen car in 2011, and hadn't been seen since.

"They took away so many of us," said Heba, whose mother's cousin also disappeared. "We know nothing about them ... They [the Assad government] burned our hearts."