Prime Minister Justin Trudeau says he is outraged to hear that Canadian hostage John Ridsdel has been killed by terrorists in the Philippines, and is vowing to hunt down those responsible.

鈥淭his was an act of cold-blooded murder and responsibility rests solely with the terrorist group that took him hostage,鈥 the prime minister said during a brief press conference in Alberta on Monday.

Trudeau said the safety of Canadians is a top priority and vowed to work with the Philippines and other allies 鈥渢o pursue those responsible for this heinous act.鈥

The prime minister offered his condolences to the family and friends of Ridsdel.

He did not take questions, however, saying that commenting further could 鈥渃ompromise ongoing efforts or endanger the safety of the remaining hostages.鈥

Fellow Canadian Robert Hall, Norwegian Kjartan Sekkingstad and Filipino Marites Flor were also abducted from an upscale resort complex on a southern Philippine island in September, by Abu Sayyaf militants.

On April 15, a video emerged of Ridsdel, 68, and Hall asking the Canadian government to pay their ransom. In the video, the two warned that they would be beheaded if the ransom was not paid by 3 p.m. Monday. The captors were demanding about CAD $8 million per hostage.

On Monday, Philippine officials confirmed that the severed head of a Caucasian man was found in a plastic bag along a street in Jolo, a town in Sulu province.

Family, friends mourn loss

Sandy Hunter, who was best man at Ridsdel鈥檚 wedding, described his friend as 鈥済regarious鈥 and 鈥渙utgoing.鈥

Hunter told 麻豆影视 Channel he will remember the good times they had together, whether sailing in France, or swimming, camping and drinking wine in the Rocky Mountains.

Ridsdel鈥檚 family issued a written statement, calling the killing a 鈥渟enseless act of violence鈥 that occurred 鈥渄espite us doing everything within our power to bring him home.鈥

鈥淛ohn was a kind and gregarious person who touched everyone he knew with his enthusiasm and generosity,鈥 the family said. 鈥淗e loved life and lived it to the fullest with his family and friends at the centre.鈥

鈥淗e was loved by all his friends and adored by his daughters, sister, and extended family,鈥 the statement went on.

Bob Rae tried to help

Bob Rae told CTV鈥檚 Power Play that he had known Ridsdel since 1966 when they attended the University of Toronto together.

The former interim Liberal leader said he had contacted Ridsdel鈥檚 sister and children as soon as he heard news of his capture, and was also involved in attempts to bring him home alive.

鈥淯p until the last minute, the last few hours, a lot of efforts were being made to connect, to communicate,鈥 Rae said. 鈥淥bviously there was talk of money involved, not by the Government of Canada or the Government of Norway, but certainly by the families,鈥 he added.

Rae said that Canada has long had a 鈥減rincipled鈥 policy of not getting directly involved in hostage negotiations or paying ransoms, in order to discourage kidnappings.

However, Rae said that 鈥渞ight up to the Prime Minister of Canada,鈥 senior officials had been regularly involved in the crisis.

Rae added that there are still 鈥渁 lot of conflicting reports about exactly what happened,鈥 but that Ridsdel showed 鈥渁n enormous amount of courage and dignity and honesty throughout the process.鈥

Rae said he will remember his friend as adventurous, gregarious man with an 鈥渋nsatiable curiosity,鈥 which led him first to journalism and later to jobs in the mining and energy sectors.

Interim Conservative leader Rona Ambrose issued a statement Monday calling Ridsdel鈥檚 killing 鈥渟hocking and saddening鈥 and offering her condolences to his loved ones.

鈥淚ncidents like this should remind all of us that the threat of terrorism remains very real,鈥 the statement went on. 鈥淲e must stand with our allies in solidarity against terrorism, which remains the greatest challenge that the world faces today.鈥

With files from The Associated Press