Kerry Jernigan was off duty late on a Thursday night when the call came on the Riverdale Park murder. It was his turn on the homicide rotation, so he drove to where a man had been shot for getting between a robber and a wad of money.

By the time Jernigan arrived, Ricardo Jimenez Santa-Maria was dead at the hospital. His mistake had been reaching for his cell phone just as the gunman was about to snatch $600 from his sister-in-law. The shot the guy squeezed off caught Jimenez in the chest.

Unaware he'd stumbled into the latest episode in what would come to be called a "one-kid crime wave," Jernigan began the methodical business of figuring out what had gone wrong in the 5400 block of 56th Place.

That part of Riverdale Park is a working-class area not known to Prince George's County police as a violent place. Once in a while someone calls the cops because guys drinking in front of one of the red-brick apartment buildings are making too much noise. Other blocks in the county are considered likely places to find trouble, but not this one.

By then the "one-kid" rampage had been underway for almost a month, and the puzzle pieces were falling into place. And even as he committed his final crime three days later, a police stakeout squad was waiting for Anthony James Cole to come home to his parents' house in Capitol Heights.

There were 148 homicides in Prince George's last year, foreshadowing a steady increase in violent crime that has continued this year. But there was nothing to compare to the sustained burst of mayhem and intimidation committed by one teenager between Aug. 15 and Sept. 12 last year.

In 29 days, the skinny youth, then 17, killed two people, tried to kill two more, assaulted at least a half-dozen others and held a man at gunpoint while sexually abusing his girlfriend. All of this occurred as he went about the business of robbing people at gunpoint, including eight robberies he would plead guilty to and an additional two dozen or so that police say were his work.

And as each day went by, Cole got bolder and more violent.

"It is typical that he, like any serial killer or thrill killer, just got more crazed and things got more personal," Jernigan said. "Who knows? If things hadn't have happened the way they did, we might have had even more homicide victims after the sexual assault."

After eight years in homicide, Jernigan recognized that the Riverdale Park murder had the look of a riddle with no easy answer: an armed robbery gone bad with the gunman wearing a mask, and nothing to go on except the 9mm bullet that went astray and got lodged in a wall.

It was Jernigan's fifth homicide case -- and the county's 99th -- so far that year. When seemingly random killings come in bunches, detectives don't always have time to compare one to the next, but if they had, they would have noticed that slaying No. 97 looked about the same.

In that one, four days earlier, a robber in a wool mask shot Baudillio Ramos Osorio, 37, in the back outside a Bladensburg apartment building, and he turned the gun on a couple of people who shouted at him out the window, firing 9mm slugs into the wall.

As Cole would tell it later, his crime wave came about as the result of an accident. He hadn't meant to step on a crack dealer's stash of little glass bottles, but that little mishap had put him $500 in debt, and he said the dealer vowed to shoot him if he failed to pay up.

Cole said he began sticking up cabdrivers.

"I never robbed any people," Cole would later tell police, "just cabdrivers. They are the only people who are guaranteed to have money."

Later, he targeted Hispanics, he told police, simply because they tended to be out late at night. All the crimes were committed in his old neighborhood, where he knew every street and shortcut and could melt into the night.

His mother and father raised him in that area, and except for some time with his father's family in North Carolina, he'd spent his entire life there. It's also where he began getting into trouble.

When police asked him how many schools he had attended, Cole used his fingers to count.

"I went to eight schools," he said after a pause to recollect. "I have been suspended from all of them."

Then he corrected himself. Nine. He had gone to nine schools. He forgot the one in North Carolina. He'd been expelled from that school, too.

When he was in school, he wasn't much of a student, according to a psychologist's report filed with the Prince George's County Circuit Court. He repeated first grade, seventh grade twice and ninth grade. He started drinking alcohol every day at age 16. He began smoking marijuana regularly at age 12.

On the street, Cole went by the nickname of Mann, as in "The Man."

His strategy was to rob and run. At first, he wore gloves and a knit ski mask that made slits of his eyes. He was tall and skinny with a long face, but the black 9mm handgun made him look bigger.

All he had to do was point it at people to scare them out of their money or make them turn tail and run as fast as they could. As their fear fueled his courage, he got more and more brazen. Soon the gloves were gone, and so was the mask.

Then he started pulling the trigger. That's when he graduated from being a punk stickup kid, a "knucklehead" as one police officer called him, to a killer willing to shoot someone for a fist full of cash, not knowing whether it was $20 or $200.

Jarrel Jordan put a little pin in the map on his office wall to mark the spot each time the man with the mask and gloves pulled a stickup.

"Everything was within a half-mile to mile radius," said Jordan, one of four robbery detectives tracking a pattern of robberies that began around Aug. 15.

Jordan, 35, grew up in Prince George's and knew the streets as only someone who ran them as a child could. In early September, someone told him that there was a kid committing a bunch of armed robberies and that the kid always had a gun. The informant didn't know the kid's real name, just his street name.

It was Mann.

Trying to link a real name to Mann, police brought in another informant to look at photos of young men who had been arrested or questioned by the robbery squad.

"That's him," the informant said. "That's Mann."

Jordan turned over the photograph. On the back was the name: Anthony James Cole.

The stakeout at his parents' house lasted a few days, until Cole came home before dawn Sept. 12. The police flashed a warrant, arrested him and searched his room. They found an ATM card that belonged to the sexual assault victim. A 9mm shell casing and part of a spent 9mm bullet turned up inside a Timberland boot.

Cole admitted to several robberies but said he had never fired his gun. Police sent him to jail and the bullet out for ballistic testing against bullets found at both murder scenes.

Three days later Jernigan was sitting in a training class when his cell phone rang. It was the robbery squad; it had someone he might want to question about the murders in Bladensburg and Riverdale Park.

The video camera is tucked up in the corner by the ceiling of interview room 6 in the sexual assault unit. Covered by a dome of glass, it peered over Cole's left shoulder, taking in the whole room.

Jernigan walked in firing questions. "Drink? Food? Cocktails? What do you want? Want a soda, coffee, water?"

Cole was seated in a plastic chair at a brown table. His arms rested on the table, his legs absently opening and closing. Even in the bulky orange jumpsuit that was his prison uniform, it was clear how slightly built he was.

Jernigan was there to break him down. But first he had to earn his trust.

"Anytime you decide you don't want to talk to me no more, we're done," Jernigan told him. "Okay? You control this whole situation. Are you willing to talk to me now without a lawyer? Right now?"

Cole looked at him. "Yup," he said. There was nothing menacing about him. He spoke in a soft voice, as polite and respectful as a teenager in the principal's office.

The questions came in a slow and steady pace. Did he own a gun? Why did he own a gun? Why did he target cabdrivers? Where did he get the ATM card found in his room? What about the bullet casing found in his boot?

"You can admit what you did wrong or you can keep playing games," Jernigan said in an even voice. "You can play the lying game and the game of deceit . . . but little do you know there are many problems in front of you right now that I haven't brought up yet."

While Cole sipped his Pepsi, Jernigan gave him a lesson in DNA, telling him that he was leaving his DNA on the soda bottle. Cole put the bottle on the table. He told him they had his DNA from a crime scene.

"Tell me what happened at the lady's apartment," Jernigan said, finally.

For a moment or two, Cole didn't say a word. He was looking down at his hands, clasped in front of him on the table. Then, looking at Jernigan, he let out a little groan and said: "I don't know what came over me. I wasn't thinking at all." Then, in a voice that sounded like a kid confessing to stealing candy, he quietly recited how he had made the woman perform oral sex and then shot the man when he came to her aid.

The Riverdale Park shooting was next.

"I don't know about that one," Cole said.

Jernigan told him they had evidence of him at the scene. "You were there. You did it. . . . Let's get it all out in the air," he said.

Cole nodded, putting his head in his hands. Then he admitted that he shot Jimenez.

"There's another one," Jernigan said. He outlined the killing of Osorio, who had been shot in front of witnesses as he tried to run away from the robbery on 63rd Place.

Cole put his head on the table, took a deep breath and groaned. As Jernigan pressed on, Cole began sniffling. He said he wasn't sure which shooting the detective had described.

"Okay, well you don't shoot a person every day . . . so there has to be a memory of it in your mind," Jernigan said.

Finally the words came. "Everyone else was listening," Cole said, quietly. "And he was just looking at me, you know what I'm saying? He started going off to the building. . . . After I shoot him, I run."

A minute passed. Jernigan asked Cole if he was hungry. When the detective left the room to order him a pizza and get him a pack of menthol cigarettes, Cole put his head in his hands and cried.

About a half-hour later, Jernigan was back in the room. Cole was smoking. The tears were gone, and his voice was strong. Jernigan began asking him about the Riverdale Park shooting again, and suddenly Cole interrupted.

"He, he, he, he came through, right?" Cole asked.

"Who came through?" Jernigan said.

"The person I hit."

"That you shot?" Jernigan said. "Unfortunately, no, he died."

Cole began to cry, and for a moment or two, his muffled sobs filled the room.

"I know it's tough. I know it's tough," Jernigan said.

Cole wiped his eyes and looked at the detective. "Anybody else?"

"Huh?"

"Anybody else?" he asked.

"That died? Ah, the one on 63rd."

"Which one?" Cole asked.

"The one where people were gathered outside the apartment."

Cole cried harder now. He kept wiping at his tears as they rolled down his cheeks. "I didn't want to hurt nobody," he sobbed. "I ain't never wanted to hurt nobody. I just wanted to pay my debt."

A prosecutor called Cole a "one-kid crime wave," and a grand jury indicted him on 139 criminal counts. In June, he pleaded guilty to two counts of first-degree murder, eight counts of robbery with a deadly weapon, six counts of first-degree assault, an armed carjacking and the sexual assault. He was sentenced to two consecutive life terms in prison, plus 40 years, and is unlikely to be considered for parole for 60 years.

"I don't think this kid has any conscience," Assistant State's Attorney Fran Longwell said after the sentencing. "Pretty scary."

The brother-in-law of Edith Flores Sanchez, 43, died after an armed robbery in this parking lot in Riverdale Park.

Kerry Jernigan of the Prince George's police helped solve the crimes. He says Anthony Cole, "like any serial killer or thrill killer, just got more crazed."

Ricardo Jimenez Santa-Maria, 44, was killed when he reached for his cell phone during the robbery.