Adam Mayes is a skilled mechanic who needed a heart transplant and was obsessed with the two girls authorities suspect him of kidnapping after allegedly killing their mom and sister, a Mississippi man who was Mayes' landlord and close friend told FoxNews.com.

Danny Johnson said Mayes, the FBI's newest most-wanted fugitive, was “like a brother” to him for the last two years. Johnson told FoxNews.com that Mayes often spoke of Alexandria Bain, 12, and her sister, Kyliyah, 8, as his children and said he wanted to get custody of them from parents Gary and JoAnn Bain.

Mayes and his wife, Teresa Mayes, were charged Wednesday with first-degree murder in the deaths of Jo Ann Bain, 31, and her daughter, Adrienne, 14. Their bodies were found buried outside the Mayes' home near Guntown, Miss., a week after they were reported missing by Gary Bain. Teresa Mayes in in jail, while the FBI has offered a $100,000 reward for information leading to Adam Mayes' arrest.

Johnson thinks Mayes could be hiding in the woods with the girls.

"I'm not worried about him physically harming them, but I don't know what elements he has them in, and I'm not sure he could protect them from the elements," Johnson said. "I can't [see him] physically harming either one of those girls, but desperate people, you can't predict what they'll do.

"It's a desperate situation, but for me to say that they're in grave danger, I don't think so, but of course that'd just my opinion."

Johnson is still in shock at the knowledge that a man he knew so well is a murder suspect and the subject of an intense manhunt. He said he spoke personally to Mayes on the Monday after the girls disappeared, and the day before Mayes himself vanished.

“He told me about the mom and the girls being missing," Johnson said. "And I said, you don't have any idea where they went to, or what could've happened to them? And he told me no, that he didn't know. ... And he was very calm and collected about it.”

Mayes had suffered a heart attack, wore a heart monitor and said he would need a transplant “within a year,” Johnson said. Unlike many in the northeastern part of Mississippi, Mayes wasn't big on hunting or fishing but is an expert mechanic, said Johnson, who employed Mayes part time at a garage he owns one block from Mayes' home.

Last Friday, Teresa Mayes paid rent to Johnson's wife for June, acting like nothing was wrong. It was later that night that the two bodies were found.

Teresa Mayes told investigators her husband killed the pair at their Whiteville, Tenn., home on April 27 so he could abduct the two young sisters, according to court documents filed Wednesday. She said that after she saw her husband kill the two in the garage of the Bain home, she drove him, the younger girls and the bodies to Mississippi, according to affidavits filed in court.

For Johnson, the realization his friend may have done something evil has set in.

"It has been hard, extremely hard on me," Johnson said. "Because, I mean, it wouldn't have hurt me any more if it had been one of my brothers who had done this. We were that close. And I defended him up until the point where I had enough proof to realize that it's possible that he did this."

Garrett Tenney is part of the Junior Reporter program at Fox News. Get more information on the Junior Reporters Program here.