MANILA - (UPDATE) National Democratic Front of the Philippines (NDFP) peace consultant Randy Malayao was shot dead inside a bus in Nueva Vizcaya province before dawn on Wednesday, groups of lawyers and activists said.

Malayao's murder "on a lonely long trip on the night bus" is part of a series of attacks meant to "get those who fight the oppressive and exploitative system and who work for fundamental change fast and quick," said Edre Olalia, National Union of Peoples' Lawyers (NUPL) president and NDFP legal consultant.

"It hits you and you mourn, makes you momentarily catatonic with the shock of unbelievable," the group said in a statement. "But Randy, we will one day wake up to the dawn of hope because the nights of rage will usher a morn of justice."

Malayao, 49, was shot dead by an assailant that boarded his ride when it stopped in Aritao town around 2 a.m., said Nueva Vizcaya police director Chief Insp. Giovanni Cejes.

Police are still confirming if the victim was an NDFP consultant, he told radio DZMM.

The gunman escaped on board a motorcycle driven by a cohort, said Cejes.

The victim boarded the bus in Quezon City and was supposed to get off in Santiago, Isabela. His hometown is neighboring San Pablo, added the police official.

The Commission on Human Rights decried Malayao's slay and vowed to investigate the incident.

"His death comes at a time when voices of opposition and human rights groups are tagged as enemies, making them possible subjects of assaults," it said.

Former Bayan Muna party-list lawmakers Neri Colmenares and Teddy Casiño expressed their grief over Malayao's slay.

I am greatly saddened and angered by the killing of my friend Randy Malayao, NDFP peace consultant and Bayan Muna regional coordinator for Cagayan Valley. He was shot while sleeping in a bus on his way home. We demand justice for Randy and other victims of extrajudicial killings. pic.twitter.com/wPc4tO7Rrh

— Neri Colmenares (@ColmenaresPH) January 30, 2019

Let us light a candle in our hearts for our friend and comrade, the quintessential activist, Randy Malayao. Randy was gunned down inside the bus he was riding last night. May he rest in peace but may his death trigger our outrage for justice. https://t.co/ht6ksBGZoe

— Teddy Casiño (@teddycasino) January 29, 2019

Malayao, formerly among leaders of the Communist Party of the Philippines (CPP) in Cagayan Valley, was arrested in Cainta, Rizal in 2008.

He was accused and later acquitted of involvement in the 2001 killing of Cagayan Rep. Rodolfo Aguinaldo, a former military officer and prominent anti-communist campaigner.

Before peace talks between the government and the NDFP collapsed in 2017, Malayao attended the negotiations in Europe.

Government had halted talks citing continuing rebel attacks against state troops when negotiations were ongoing.

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