May 31, 2012 -- Despite surveillance video, eyewitness statements, and a victim clinging for life with more than 75 percent of his face chewed off, the family and girlfriend of Rudy Eugene are telling the world there is no way he could attack someone so viciously.

"I knew my son," Eugene's mother, Ruth Charles, told ABC affiliate WPLG. "Rudy will never, never do something like that. Somebody killed him, and they just go and dump him."

Police believe the meeting of Eugene and 65-year-old Ronald Poppo was a chance encounter that occurred after Eugene dumped his car in South Beach and walked 3½ miles across a causeway, stripping off his clothes in broad daylight before attacking Poppo.

Some law enforcement officials believe the dangerous new street drug "bath salts" may have played a role in the attack. It could take weeks for toxicology results to come back, however, and there were no drugs found at the scene.

Eugene's mother, who once had a violent incident with her son that resulted in him becoming the first person tasered by North Miami police, believes he was drugged and dumped in the area where he encountered Poppo and felt threatened by him.

"When you are awake you are like a confused patient," said Charles. "Whoever you see, you go and fight."

Eugene's girlfriend, who did not want to be identified also spoke with WPLG, and was with him early in the morning before the crime. She called him religious and says he told her he was leaving to visit a friend. She says she didn't find out about the attack until the following morning and finds it hard to believe that the man she wanted to marry could commit such an act.

"He did not abuse drugs," she said crying. "I don't understand. Somebody did something to him...that wasn't him."

Eugene was shot and killed by police after they say their repeated pleas to get him to stop attacking Poppo were met with growls. Poppo, who once attended New York City's elite Stuyvesant High School and dreamed of becoming president, remains in critical condition. If he survives the brutal attack, he has a long, perilous road to recovery, according to medical experts familiar with facial reconstruction. His eyes, nose, and most of his face were bitten, with one source telling ABC News he was left with little but a goatee.

"His acute situation needs to be stabilized first," said Dr. David H. Song, chief of Plastic Surgery at University of Chicago Medical Center. "Human bites are notorious for infections and if his doctors can't control it, he could lose more of his face. Whatever dead tissue remains needs to be removed down to healthy bleeding tissue."

Surveillance video reveals that for 18 agonizing minutes Poppo was disrobed from the waist down, kicked, punched, and eaten alive before police shot Eugene four times. Poppo then sat up covered in blood as three paramedics on scene quickly got him onto a stretcher, put a neck brace on him, and rushed him to the emergency room. Doctors at Jackson Memorial Hospital, where Poppo is being treated, have been tight-lipped about his medical care citing privacy laws.

"After he is stabilized you could go several routes. He may need to have free tissue transfer. That's a microsurgical free flap where you take a large area of vascular tissue from either the belly or the thigh. These areas have their own blood supply," said Dr. Song. "Then you would have to reattach those arteries and veins to the arteries and veins in the face or near the neck."

Those types of surgeries could take months to a year to perform.

Poppo could also be a candidate for a full face transplant that would take 18 to 20 hours, but he would first need a donor and lots of support.

"That is a huge investment for an institution and society," said Song. "Although the face transplant patients may look good the downside is they will have to be on expensive immune suppressive medications so that his body does not reject another person's face for the rest of his life. The cost can be hundreds of thousands of dollars a year. Someone is going to have to give him medication. He would also have to have good social support, psychiatric support. It's a huge production."

According to reports, Poppo's family assumed he was dead until the vicious attack made headlines around the world. The homeless man lived under a bridge near where he was attacked and has no money and no insurance. For the face transplant to work he would have to be placed on a strict regimen.

For now, his doctors continue to fight to save his life. His family, Eugene's family, South Florida and the rest of the world continue to question how anything like this could happen.