CAIRO – Violent protests erupted in Tahrir Square once again as night skies were lit up by the arc of Molotov cocktails and the thump of tear gas canisters being fired into the crowd.

Thousands of protesters clashed with police into the early hours of the morning in a flash fire of anger ignited by a gathering of bereaved families to honor some of the 840 people killed in the Jan. 25 revolution that led to the toppling of Honsi Mubarak.

It was unclear what precisely triggered the clash that stretched into early Wednesday, but the protests came amid calls for justice for those killed by police during the pro-democracy protests that forced Mubarak to step down after 30 years of widespread police brutality and corrupt, autocratic rule.

In an aggressive attempt to quell the protests with tear gas and rubber bullets, police in full riot gear appeared to be asserting themselves in a way not seen since the end of the revolution. And protesters in the square seemed equally defiant in refusing to allow them to do it.

The clashes resulted in approximately 20 injuries, according to an ambulance worker on the scene.

Gamal Abdel Raqim, 44, who works in the finance department for a clothing store, hardly looked the part of a revolutionary, but with his eyes still stinging from tear gas, he said, “Half a revolution is a coffin … If you are fighting with a powerful man, you have to make sure you knock him down.”

“What’s happening is police are trying to reassert authority in the Interior Ministry,” he said, nodding in the direction of the ministry which is located just off the square and around which the police were amassing.

“And the people are saying “no” to that,” he added.

As he spoke, the crowd suddenly surged forward amid cheering as the police appeared to retreat down a side street, moving away from the protesters but appearing to retrench around the ministry.

In the center of Tahrir Square, a father named Ahmed stood holding his son, Mohammed, 7, who was waving an Egyptian flag.

“What you are seeing is that Mubarak’s power is still in place. We can’t stop now … My son was here for the revolution and when he saw what was happening on TV, he said he wanted to come,” said Ahmed, who did not provide his last name.

Asked if it was dangerous to bring a 7-year-old to a violent demonstration, he said, “I think he should be here.”

On a back street a fearful looking police man dressed in riot gear and clutching a rifle used for firing tear gas canisters, said, “We are not killers. The police try to protect the people, the ministry. And here we are only defending ourselves.”

As ambulances with sirens blaring rushed in to pick up the wounded, the muffled crack of police firing rubber bullets caused the crowd to rise up in chants of “Alla hu Akhbar!” or “God is great!” And from a loud speaker atop the minaret of the mosque just off Tahrir Square, an imam preached:

“To the shebab, you must not leave the square. To the police, leave the square and pull back. I am calling on the noble youth of the revolution not to leave the square.”

This was my first day of reporting on the ground and earlier in the day, I was just starting to feel comfortable that post revolutionary Egypt was finding its way forward to democracy. It is my first time back since I was here covering the revolution for GlobalPost and PBS FRONTLINE. I’m here now with FRONTLINE cameraman Tim Grucza to do a follow-up story.

But by late at night, Tim and I were once again rushing to Tahrir Square to cover violent clashes between police and protesters and all the intensity and adrenalin of those heady days of the revolution came rushing back.

What seemed clear last night in looking at the thousands of predominantly young men gathering in the square will keep on fighting for justice and dignity until the country forges ahead with elections, a new constitution and the demands of the protests are met.

These are young men who are increasingly educated but vastly under employed, reflecting a demographic surge of youth who are the force behind the Arab Spring from Egypt to Tunisia to Libya and beyond. They are young men who postpone marriages into their late 20s because they simply do not have the money for a wedding. They are bound by traditions and impatient for change. And they have risked it all in the name of revolution.

The question now is where this revolution ends and what a new Egypt will look like when its combustible energy winds down.

By 4 a.m., the clashes were continuing as morning was approaching.