A Florida native, born in 1946, Knowles logged his first arrest at age 19, spending roughly six months of each year thereafter in jail, on various convictions for burglary and auto theft. He was serving time in Raiford when he began corresponding with California divorcee Angela Covic, and she visited the prison long enough to accept his proposal of marriage, shelling out money for lawyers to win his release. Parole came through in May 1974, and Knowles flew directly to San Francisco for the nuptials, but Covic had changed her mind, warned off by a psychic who foresaw the entry of a new, dangerous man in her life. The night she dumped him, Knowles allegedly went out and killed three people on the streets of San Francisco, but his claim has not been verified.

Back home in Jacksonville, Knowles was jailed after a bar fight, but he picked a lock and escaped on July 26, 1974. That night, he invaded the home of 65-year-old Alice Curtis, leaving her bound and gagged as he ransacked her house for money, finally taking off in her car. She choked to death on the gag, but Knowles hung around town for a few days, using her vehicle, until police connected him with the crime and his picture began turning up on TV. Preparing to drop the hot car on a quiet residential street, he spied 11-year-old Lillian Anderson and her seven-year-old sister Mylette, recognizing them as friends of his mother. Convinced the girls had seen him and would notify police, he kidnapped both of them and dumped their strangled bodies in a swamp outside of town.

The next day, in Atlantic Beach, Florida, Knowles broke into the home of Marjorie Howe, strangling her with a nylon stocking and stealing her television set. His next victim was a teenage "Jane Doe" hitchhiker, raped and strangled for sport as he drifted aimlessly, working his way north. On August 23, he invaded the home of Kathie Pierce, at Musella, strangling her with a telephone cord while her three-year-old son looked on, leaving the child unharmed.

On September 3, Knowles met businessman William Bates at a tavern in Lima, Ohio, sharing a few drinks before he strangled Bates and dumped his body in some nearby woods, where it would be discovered in October. Stealing money, credit cards, and Bates's car, Knowles made his way to Sacramento, back through Utah, pausing at Ely, Nevada, long enough to murder campers Emmett and Lois Johnson on September 18.

Three days later, passing through Sequin, Texas, he spotted a female motorist stranded at roadside and stopped "to help," raping her before he strangled her to death and dragged her body through a tangled barbed wire fence. On September 23, he met beautician Ann Dawson in Birmingham and instantly caught her fancy; they traveled together, at her expense, until Knowles tired of the game and killed her September 29. Her body has never been found.

Knowles drifted on through Oklahoma, Missouri, Iowa and Minnesota, apparently keeping his nose clean, leaving no bodies behind. By October 19, he needed a "fix," and he found it in Woodford, Virginia, barging into the home of 53-year-old Doris Hovey, shooting her dead with her own husband's rifle, then wiping his prints from the gun and placing it beside her body. Afterward, police would find no signs of sex or robbery to offer them a motive in the case.

Still driving Bates's stolen car, Knowles picked up two hitchers in Key West, planning to kill them both, but his scheme went awry when a policeman stopped him for traffic violations. The careless officer let Knowles go with a warning, but the experience had shaken him. Dropping his passengers off in Miami, Knowles phoned his lawyer for advice. Rejecting a suggestion of surrender, he met the attorney long enough to hand over a taped confession, then slipped out of town before police were informed of his presence.

On November 6, in Macon, Georgia, Knowles befriended Carswell Carr and was invited home to spend the night. Over drinks, he stabbed Carr to death and then strangled Carr's 15-year-old daughter, failing in his attempt to have sex with her corpse. In the wake of his flight from Macon, Knowles was also suspected in the November 2 murder of hitchhiker Edward Hilliard, found in some nearby woods, and his companion Debbie Griffin (still, among the missing).

Bar-hopping in Atlanta on November 8, Knowles met British journalist Sandy Fawkes, impressing her with his "gaunt good looks." They spent the night together, Knowles unable to perform in bed, and he failed repeatedly at sex over the next two days, suggesting possible impotence with a willing companion. They separated on November 10, but Knowles picked up one of Sandy's friends, Susan MacKenzie, the next day, demanding sex at gunpoint. She escaped and notified police, but when patrolmen tried to stop him, Knowles brandished a sawed-off shotgun and made his escape.

In West Palm Beach, he invaded the home of invalid Beverly Mabee, abducting her sister and stealing their car, dropping his hostage off in Fort Pierce, Florida, the following night. A police officer recognized the stolen car next morning and pulled Knowles over, but Knowles was faster on the draw. Taking the officer hostage, he drove away in the patrol car, using its siren to stop motorist James Meyer, switching cars a second time. Burdened with two prisoners now, Knowles handcuffed both men to a tree in Pulaski County, Georgia, and shot each one in the head at close range. A short time later, Knowles tried to crash through a police roadblock, losing control of his car and smashing into a tree. A chaotic foot chase ensued, with Knowles pursued by dogs and helicopters, finally cornered by an armed civilian on November 17. In custody, he claimed 35 murders, but only 18 could be verified.

On November 18, he was killed while trying to escape as he was being transported back to the site of his arrest, where he claimed he would lead officers to the location of the gun missing from the killed Florida Trooper.