When his colleagues found him, his pockets had been emptied and his Secours Catholique-Caritas France t-shirt removed.
Villagers reported seeing Mr Sukaka, who was a Congolese national, stopped by two men wearing Congolese army uniforms before he was killed.
"Unidentified gunmen opened fire on their car as soon as they left for a trip to conduct surveys," Dahir Mohamed, one of their colleagues, said by phone from the region."We don't know who is behind the attack and the gunmen escaped after they killed the men," local elder Hasan Haji Idris said.
Source: Two Somali aid workers and their driver shot dead
For other aid worker deaths this year see the Aid Worker Fatalities 2009 map.
Three masked gunmen shot and killed 44-year-old Somali national Ibrahim Hussein Duale, while he was monitoring school feeding in a WFP-supported school in Yubsan village six kilometres from the Gedo region capital of Garbahare. Witnesses say the gunmen approached him while he was seated, ordered him to stand up and then shot him.
Some 300,000 Sudanese refugees who have fled the Darfur conflict live in camps in Eastern Chad. 187,000 Chadians displaced by fighting in Chad have also sought sanctuary in IDP camps in the area.
Rebels attack eastern Chadian town, aid worker says
Officials: Rebels attack in eastern Chad