By KATE BRUMBACK ,  Associated Press

MADISON, Ga. (AP) — The FBI is expanding the search for two inmates sought in the killing of their guards on a prison bus in Georgia, and a sheriff said Thursday the fugitives could be halfway across the country by now.
A reward for information leading to the arrest of Donnie Rowe and Ricky Dubose rose to $130,000 after contributions from more law enforcement agencies, Putnam County Sheriff Howard Sills said.
"We need the eyes and ears really of anybody in this country to be on the lookout," Sills said.
"It's not just because of the crime, it's because the public is in grave danger," he added. "These are dangerous, seriously dangerous, vicious hoodlums that need to be apprehended."
Authorities said the last sign of the two fugitives remains the theft of a 2008 white Ford F-250 pickup truck with the Georgia tag BCX-5372 from a rock quarry. Sills said it was stolen between 11 p.m. and midnight Tuesday, about 12 hours after they ransacked a house 9 miles away to gather food and change from their prison uniforms.
Sills said the Honda Civic they carjacked at the killing scene was hidden in some woods, and they walked to the quarry from there.
"They're doing like most escapees do. They're stealing cars. We know they did a burglary. We know they took food there. We know of no great amount of money, but there may have been some money there the victim didn't know about," the sheriff said.
The FBI, the U.S. Marshals Service, and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives are all involved.
"It has become a nationwide search," said David LeValley, who runs the FBI office in Atlanta.
Sills wouldn't comment on whether the other 31 inmates left locked inside the bus with the slain guards' bodies revealed how the escapees managed to get out of the secure compartment. Department of Corrections Commissioner Greg Dozier wouldn't comment on that part of the investigation either.
Sills said there's no visible evidence — an apparent reference to video from a security camera on the bus — showing that other inmates participated. And he praised the other inmates for aiding the initial search.
"Yes, they have been interviewed," Sills said. "They provided the most vital information at the most crucial time."
Authorities said the two inmates overpowered and killed Sgt. Christopher Monica and Sgt. Curtis Billue early Tuesday on a bus that should have been secured as it carried inmates between prisons. The pair then carjacked a driver who pulled up behind the bus, and fled in his Honda Civic down state Highway 16 in Putnam County, southeast of Atlanta.
Signs of the fugitives turned up hours later and 25 miles north, in Madison, where authorities found the house ransacked and, hours later, the pickup stolen. By then, the trail had gone cold.
Both Sills and LeValley appealed for the public's help, urging people to call 911 immediately with any sign of them, rather than try to handle escaped inmates believed to be carrying the guards' 9 mm pistols.
Dubose could have trouble hiding his prominent tattoos, which include a crown above his right eyebrow and a star below his right ear, the word FACE above his left eyebrow, and graffiti-style letters across his neck. Sills said Dubose also has "ghost" tattooed on his right forefinger and "face" on his right pinky finger — signs of membership in the Ghost Face Gangsters.
The sheriff was asked whether the prison gang or its associates could be helping the fugitives elude capture.
"These people have relatives, these people have friends. There's an infinite number of people that may well be helping them outside," the sheriff said. "If somebody is helping them and we find out who they are, they will be prosecuted as participants in this crime, there's no doubt about that."
Rowe, 43, has been serving life without parole since 2002, and Dubose, 24, began a 20-year sentence in 2015. Both were convicted of armed robbery and other violent crimes, and they've been cellmates more than once in Georgia's prisons.
Monica, 42, and Billue, 58, were both transfer sergeants at Baldwin State Prison. Monica had been with the Georgia Department of Corrections since October 2009 and Billue since July 2007.
Dozier said that when he was alerted to their deaths, "The pain and anguish that was in the toes of my feet went up to my heart."
"The impact of these cowardly acts is far-reaching," the commissioner added. "Sgt. Monica leaves behind a wife, two daughters, a community that loves him, people that respected and looked up to him ... Sgt. Billue leaves behind two sisters, five brothers, a father and some children."
"These men were impactful to their communities, their families and this agency. We cannot replace them," he said.
The FBI is rolling out "a significant media effort" including "a nationwide billboard campaign" to appeal for help from the public, LeValley said. The billboards will advertise specifics about the reward and a nationwide tip line: 877-926-8332.
LeValley stressed that the reward is for information leading to an arrest, saying: "We do not offer rewards for someone to be brought in dead or alive."
Making a direct appeal to the two fugitives, the sheriff said: "You need to surrender. You will be apprehended."