In the deep darkness of the early morning, on a prison bus that became a rolling crime scene, Philip E. Parker Jr., 20, and Kevin G. Johns Jr., 22, were together one more time, the last time.

They were among 35 inmates who sat shackled to themselves, wearing three-piece suits of ankle, waist and wrist chains. In a cage at the front - and another at the back - sat two guards not 10 feet from the nearest prisoner they were to be keeping watch over, though it was hard to see much.

They were almost at the end, 60 miles into a 75-mile haul on a routine trip across a desolate Interstate 70 from Hagerstown to Baltimore as it neared 4 a.m. Feb. 2. That's when a guard heard a commotion, shined his flashlight and saw blood on the shirt of a prisoner moving about the aisle.

No one stopped the bus. No one moved closer to investigate. Safety regulations wouldn't allow it. Not until the bus arrived at the prison for the worst criminals in the state would officers make the discovery they suspected - one inmate, still tightly bound is his own manacles, strangled by the chains of another.

The lifeless 6-foot-6 body of Parker, who was serving three years for unarmed robbery, was splayed on the floor.

Sitting behind Parker was Johns, a murderer twice over - both of his victims strangled, one with a belt, one with bare hands.

Just hours earlier, the 5-foot-7 Johns had been sentenced to life for the second time in two years, warning in a Hagerstown courtroom that he would likely kill again if he wasn't treated for his psychiatric problems.

Less than two weeks after the killing, the state Division of Correction still isn't saying what happened on the bus, and indeed, all of the inmates who were in the locked bus compartment with Parker are potential suspects. No charges have been filed, and few answers have been forthcoming.

But the focus of the investigation has swung toward Johns, law enforcement sources have acknowledged. A guard on the bus saw blood on Johns after the slaying, and the prison chaplain told Parker's parents that the suspect had blood on his wrists. Johns' lawyer, seeking to protect his client's Fifth Amendment right against self-incrimination, wrote a letter to prosecutors warning them not to question his client because Johns "might be a suspect."

A review of court records and interviews with correctional authorities, witnesses, lawyers and family sheds some light on how these two ended up taking this fatal journey together.

"I know they're working on it, but I need to know what happened to my baby so I can sleep at night," said Melissa Rodriguez, Parker's 38-year-old mother. "If something like this happened to our child [on our watch], we would be in jail for neglect."

Kevin Gregory Johns Jr.

Kevin Gregory Johns Jr. was born Nov. 4, 1982, at St. Agnes Hospital.

His mother was 18, a drinker who took her first sips at the age of 13. His father became a homeless alcoholic who lived in shelters after separating from his mother. While they were together, life was violent and chaotic. They would have three more children, but it didn't turn them into a family.

This picture of Johns' life is painted by a psychiatric evaluation done for the public defender's office in 2002 and 2003 in the months after he was charged with killing his 34-year-old uncle, Robert Lee Percell.

Prosecutors say Johns killed Percell because he wouldn't give his nephew money. In statements to police, Johns says it was more than that - Percell had wrongly accused him of stealing $100, Percell had picked fights with Johns' parents, Percell had molested him as a baby.

The Department of Social Services first came into Johns' life when he was 3, taking over full responsibility for raising him when he was 6 after his stepfather was found to be abusing him. He would be in and out of foster care and institutions until he turned 18.

He was diagnosed with many things. Fetal alcohol syndrome. Lead poisoning. Attention deficit disorder. Depression. Post-traumatic stress disorder.

There were too many medications to name, drugs that were always being changed.