The federal reward brings the total amount of money offered for information leading to Mayes' arrest to $175,000, Ford said. He continues to evade a small army of 17 law enforcement agencies and hundreds of searchers.
Police said Teresa Mayes told them she was in the Bains' garage where Adam Mayes killed Jo Ann and Adrienne Bain.
The mother, Mary Frances Mayes, has been charged with four counts of conspiracy to commit especially aggravated kidnapping.
Authorities describe Adam Mayes as a white man with blue eyes and brown hair. He weighs 175 pounds and is 6 feet, 3 inches tall. He recently cut his hair and may have done the same to the missing girls.
In security camera video shot April 30 at a convenience store near his home, Mayes is seen with short hair and a goatee. Nick Bargouthi, the clerk seen in the video, told HLN's "Issues With Jane Velez-Mitchell" that Mayes was a frequent customer.
"He walked in, went in and bought a Coke," Bargouthi said. "I noticed he cut his hair, got rid of his pony(tail). When I asked him, he said, 'Yeah, it was too hot.' But he kept all his facials on. And then he walked out."
He was last seen May 1 in Guntown. While the search is centered around his hometown, he also has connections to Arizona, Texas, Florida and the Carolinas, the FBI said.
Adam and Teresa Mayes have been married for 11 years and lived in Guntown, said Johnson, Teresa Mayes' attorney. She said she has asked for a mental health evaluation of her client.
Bobbi Booth, Teresa Mayes' sister, spoke to CNN's Anderson Cooper this week about Adam Mayes and his relationship with her sister, who she said has mental health problems.
"I've known Adam for at least 25 years, and he's always been weird and unusual ... but I never dreamed he would do something like this," she said.
She described him as aggressive and not trustworthy. He beat and threatened to kill her sister, said Booth, who pleaded with him to "do the right thing."
"Just let the children go. This has gone on way too far, and we need to figure out what's going on, and it's not fair to the children," she said.
Authorities tried to interview Mayes soon after Gary Bain reported his wife and the girls missing April 27 in Whiteville, a western Tennessee town of 4,600 people. However, Mayes fled, officials said.
Mayes may be using the alias of Christopher Zachery Wylde or Paco Rodrigass, his Facebook profile name, according to the bureau.
Ellen Fulghum, a guidance counselor at the high school Adrienne Bain attended, told HLN there was "a dark cloud" over the school and community.
"It's just a heaviness. Our hearts are heavy," she said.
"It's one of those situations where, as adults there's no way we can wrap our minds around something like this," Fulghum added. "It's very hard to help children through a grieving process when it is something of this nature."
-- HLN's Natisha Lance contributed to this report
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