An Albanian court acquitted two state security guards Thursday on charges of killing four people during a 2011 anti-government protest, prompting the opposition to stage a parliament walk-out.
Judge Besnik Shehu cleared the two senior officers of the elite Republican Guard, Ndrea Prendi and Agim Llupo, who had been accused of shooting at protesters gathered in front of the government seat in Tirana in January 2011.
Shehu said prosecutors -- who had demanded 23 and 25 years prison terms for Prendi and Llupo respectively -- had failed to prove the charges.
The court also acquitted Kasaj Armando of concealing video evidence of the incidents during the opposition protest against alleged electoral fraud and corruption.
The verdict provoked strong reaction.
"Today, injustice has triumphed over justice," said Renato Myrtaj, son of one of the victims.
He warned of "revenge if those guilty of murders are not convicted," in what could be seen as hinting to Albania's centuries old tradition of "vendetta" or blood feud.
Prosecutors, who had called the US Federal Bureau of Investigation for assistance during the probe, did not say whether they would appeal.
The US embassy in Tirana said it was "dismayed" by the court's decision.
"Regrettably, today’s verdict has undermined confidence in the ability and willingness of the Albanian judicial system to deliver justice in an impartial, transparent manner," the embassy said in a statement.
The opposition Socialist party walked out of the parliament session in a protest against the verdict.
"The killing of four protestors is a state crime and I assure families that their deaths would not be forgotten until justice is done," Socialist leader Edi Rama said.
Albanian right-wing Prime Minister Sali Berisha said he "did not want to comment on any verdict."
Berisha's party and the opposition have blamed each other for being behind the violence during the protest.
The verdict will further aggravate relations between the government and the opposition in Albania ahead of general elections due in June.
Ever since the previous vote in 2009, the Balkan country has been in a deep political crisis that has halted Albania's path towards EU membership.