The People's Army and a network arm of the People's Democratic Force to Overthrow Thaksinism (Pefot) yesterday demanded police speed up the investigation into the shooting of security guard Sutin Tharatin.
UNDER SCRUTINY: Election Commission staff at the Ratchathewi district office check ballot papers and boxes amid tight security.
Sutin, 52, was shot dead and 10 other people were injured last Sunday in an attack near Wat Sri Iam in the Bang Na area where he and other protesters went to block people from entering a polling station for advance voting.
About 50 protesters from the People's Army, led by Somkiat Pongpaiboon, and the Energy Reform Network, a Pefot network group led by Rawee Mashmadol, gathered at Shinawatra Tower 3 on Vibhavadi Rangsit Road to call for justice for Sutin.
They said there had been no progress in the investigation by police despite the fact that video clips released on social media clearly showed a suspect.
Dr Rawee read a statement urging police to summon the male suspect in a camouflage jacket who appeared in the clips aiming a handgun at a six-wheel truck on which Sutin and other protesters were standing.
The man wore a military-print jacket and denim pants, according to the video clips.
"Evidence from the video clips is clear in this case. Police don't need to wait until they finish questioning witnesses," Dr Rawee said.
"The incident happened under the government's emergency decree. How could police let this group of men carry weapons?"
The group believed a subordinate of a politician was involved in the attack.
The protesters burned coffins with photos and the names of caretaker premier Yingluck Shinawatra, caretaker Energy Minister Pongsak Raktapongpaisal and Energy Ministry secretary-general Suthep Liamsiricharoen attached to them.
The group said Sutin had campaigned over national energy reforms among other anti-government campaigns.
One of those injured in the attack, Wichan Sukbangnop, 53, from Nakhon Si Thammarat, appeared at the protest.
He was with Sutin on the six-wheel truck during the attack. His left cheek was grazed by a bullet and his left hand was wrapped in a splint after having an operation to get another bullet out.
"I believe evidence is available," Mr Wichan said. "Anti-government protesters have been attacked many times. But in none of the cases have they found the criminals."