Sarawak PKR chairman Baru Bian described his deputy, the late Peter Ato Mayau, as a principled man who believed in the struggle for justice.
Siti Kuzaimah Annuar (surveyor) and Henry Lay (engineer) were also killed in the crash.
The pilot of the helicopter Reco Steger, 35, a german, survived the crash.
The helicopter is owned by local businessman Sng Chee Hua.
They were on their way to Nanga Merit, Kapit to inspect a project when the incident occurred.
Ato, an engineer and contractor, was being groomed to contest the Mambong seat in the coming general election.
In the state election last year, he did pretty well against Roland Sagah of Pesaka Bumiputera Bersatu (PBB) party in the Tarat constituency, which is part of Mambong parliamentary constituency.
He polled 4,292 votes as against 6,287 votes secured by Sagah.
This is the second death involving PKR leaders.
Last April Sharkawi Nahri was killed in a road accident at Bukit Begunan. He was earmarked to contest the Batang Sadong constituency against the incumbent Nancy Shukri.
Ato’s remains are now at the Kuching mortuary pending a postmortem.
Ato leaves behind wife Agnes Batang and three children, a son aged 25, and two daughters, aged 20 and 18.
Expressing his shock, Baru Bian, who is Sarawak PKR chief said: “I am shocked and deeply saddened by the news that my vice-chairman Peter Ato Mayau has passed away after a helicopter in which he was traveling crashed into a river.
“The news of the crash came to me last night as I was attending a prayer rally at Buduk Nur, Ba’ Kelalan and I have just been informed that Peter’s (Mayau) body was recovered this (Saturday) afternoon.
“I am presently making my way back to Kuching,” said Bian.
Bian who is also Ba’Kelalan assemblyman described Mayau as a “principled man” who was working “quietly in Mambong”.
“Peter (Mayau) was a quiet but principled man who believed in the struggle for justice and fairness for the people.
“He was quietly working and campaigning in the Mambong parliamentary constituency in preparations for the coming General Election. We thank him for his contribution to the party and to the people of his area.
“We will miss him as we carry on with our cause. We share in the grief of Peter’s (Mayau) family as they mourn the loss of a loved husband and father. We pray for them and with them,” said Bian.
He also extended his sympathy and prayers to the families of the other two victims, Siti Kuzaimah and Law.
Bian also took the opportunity to urge the authorities to to look into the “overall” safety procedures of helicopter services in the state.
“I wish to add here that there have been too many helicopter accidents in Sarawak over the past few years and I request that the authorities carry out a thorough investigation into the cause of the crash, and look into the overall safety procedures of helicopter services in the state,” he said.
Since 2002, there have been 11 helicopter crashes in Sarawak, killing 26 people. Among the notable person killed was an Assistant Minister and the Ba’Kelalan Assemblyman Dr. Judson Sakai Tagal on July 12, 2004. In that accident seven were killed.