With former boxing champion and opposition leader Vitali Klitschko looking on stony-faced, Parasiuk, from the western city of Lviv, made an electrifying impromptu speech denouncing the opposition for "shaking hands with this killer".

No one was going to wait for an election later in the year, he said. Yanukovych had to get out of town by the following morning or face the consequences.

To the dismay of opposition leaders, Parasiuk's emotional address - he broke down on several occasions as he remembered dead comrades - touched a chord deep within the thousands in Independence Square who roared their approval.

The opposition had failed to sell their achievements to the Maidan, the name for both the square and the country's protest movement.

An agreement, painstakingly negotiated with EU foreign ministers over a sleepless night, was effectively dead.

The writing was on the wall for Yanukovych. He flew out of Kiev by helicopter that night, Ukraine's acting interior minister said, and a few days later was on the run, being sought for "mass murder".

"Opposition leaders said they had agreed that there would be early elections in December. This was the Ukrainian people's last drop of patience," Parasiuk said in an interview.

"Emotions were overflowing because we had lost a great number of people. Suddenly these politicians come and say: 'Yanukovych will stay as president and there will be elections.' I have a clear position. Yanukovych is a terrorist, Terrorist Number One, for Ukraine," Parasiuk said.

That Friday night, Yanukovych set off on a zig-zag by helicopter and car across eastern and southern Ukraine, looking either for a safe haven or a flight out of the country.

Some believe he may have already decided he was going to flee even before the Maidan gave thumbs-down to the agreement.

Ukraine's opposition, buoyed by the direct intervention of three EU ministers, from Germany, Poland and France, had signed an agreement that seemed to meet many of their demands.

It provided for early elections, a national unity government and return to a previous constitution that would take away from Yanukovych control over the appointment of the prime minister and make-up of the government, and return it to parliament.

Almost immediately, the parliament, where Yanukovych's grip had been weakened by desertions by deputies from his Party of Regions, began voting many of these proposals into law.

But when opposition leaders took the deal to the Maidan for definitive approval, it blew up in their faces - thanks to Parasiuk's emotional intervention.

Klitschko and other opposition leaders had already spoken of their achievements in putting a deal together.

But there was a mixed reception from the Maidan. Booing, whistling and cat-calls gave Parasiuk his cue.

As the crowds carried open coffins of victims to the stage where he and opposition leaders stood, Parasiuk, his voice breaking, jumped to the microphone.

"We ordinary people are saying this to the politicians who stand behind us: 'No Yanukovych is going to be a president for a whole year'," he said to roars of support from the crowd.

"Our kinsmen have been shot and our leaders shake hands with this killer. This is shame. Tomorrow, by 10 o'clock, he has to be gone," Parasiuk declared.

Yanukovych was, in fact, gone long before that. Diplomatic insiders say he may already have had doubts about whether the agreement could hold. Benefiting from intelligence on the streets, he knew how the wind was blowing.

Two of the three main opposition leaders - former economy minister Arseniy Yatsenyuk, now prime minister, and far-right nationalist Oleh Tyahnybok - left the stage quickly after Parasiuk's speech. Klitschko returned and apologised for shaking hands with Yanukovych.

Though ousted by the new parliament, Yanukovych, appearing in the town of Kharkiv the next day, issued a televised statement saying he was still president. But the new authorities last Monday said he was now wanted for "mass murder".

Some reports had him hiding in a monastery in the country's east. He might be in Crimea, others said, possibly aboard a ship of Russia's Black Sea fleet. On Friday he emerged in Rostov-on-Don, southern Russia.

If Parasiuk had not made the intervention he did, someone else would have, one diplomat opined.

Looking back on that heady Friday night, Parasiuk, who headed a "self-defence" unit with a membership of between 40 and 130 fighters, defended his sharp criticism of Klitschko and the other opposition leaders.

"Everything that had been achieved had been by the people of the Maidan. But they had achieved nothing," he said in a restaurant in downtown Kiev.

Parasiuk said he had participated "actively" in clashes with police, though he declined to say what weapons he had used.

He defended the power of the Maidan with the passion of an 18th century French revolutionary. Asked when Kiev's barricades would come down, he replied: "If the Maidan disperses, politicians will stop being afraid. We are not going away. We will not allow a repeat of what happened in 2004," he said.

He was referring to the orange revolution of 2004-5, which stopped Yanukovych's first bid for the presidency but produced governments that collapsed amid in-fighting and allowed him to come to power in 2010.

He spelled out a message that Ukraine's emerging leadership may have to heed carefully as it strives to make a peaceful transition to a post-Yanukovych order.

The new authorities, he said, must understand that the Maidan is the real power, not the 450 parliamentary deputies.

"My declaration from the stage had one aim: to tell the opposition: 'Understand this. That if you do not fulfil our conditions, then things will be as we decide, not as you decide.'

"We simply told them: 'Lads, act decisively because if you don't, we will,'" Parasiuk said.