"Guns are one of the most serious issues we have to address," said Paul J. Fink, who chairs a multi-agency group that has reviewed every youth homicide in Philadelphia since 1995.

Their study found that guns were involved in 91 percent of killings involving 18- and 19-year-olds and 59 percent of those younger.

"People are going to get killed," said Bilal Qayyum, a leader of Men United for a Better Philadelphia, an antiviolence group. "There's going to be stabbings, bats, but the easy availability of guns is creating this explosion. "

Death from argument

On the streets of Philadelphia, feuds, arguments and even petty squabbles often escalate and end in death, the Inquirer's analysis shows. Of the 129 young people killed in the city since January 2000, 39 died as a result of an argument, according to police statistics.

Marquis Harris was shot in the head, police say, because someone believed the boy had broken the windshield of his Toyota Camry.

Marquis, 13, was out with his twin brother, Marc, and friends at 8:30 p.m. last September. He had just ordered a water ice when three men accused him of damaging the car.

"No, no, no. It wasn't me," witnesses said the boy cried as the men confronted him outside a Southwest Philadelphia restaurant.

One man fired and Marquis fell to the ground. As he lay on the sidewalk, witnesses said, the gunman fired again, putting a bullet in the boy's head.

Two of his friends, ages 15 and 16, were shot and wounded during the attack. Two men have been arrested and are being held without bail.

Penn's Anderson said many arguments stem from a street culture where the "rules of the code," rather than a system of civil law, are enforced.

For instance, with a scarcity of cash in the inner city, he said "there are numerous everyday exchanges, bartering, the outright loaning of money, as well as illegal enterprises such as the drug trade. . . . The policing mechanism that most often matters is street justice, essentially an eye for an eye. "

Death by fire

This year alone, arson claimed the lives of five children, four of them in a single blaze that also killed two adults.

Since 2000, 18 children have died in arson fires, a common weapon, according to The Inquirer's analysis.

On Oct. 9, a fast-moving fire swept through a house in the 3200 block of North Sixth Street, killing its owner, Marcella Coleman, 54, and her niece, Tameka Nash, 33.

Also killed were four children - Sean Anthony Rodriguez, 15; Tajh Porchea, 12; Khadijah Nash, 10; and Damir Jenkins, 15 months.

Police, who have yet to make an arrest, believe that the fire was set by members of a violent drug organization to send a message to a dealer who was cooperating with federal authorities. The victims were relatives of Eugene "Twin" Coleman, who agreed to provide the FBI with information about a multimillion-dollar cocaine ring allegedly headed by Kaboni Savage.

Although drug rings have long used violence to intimidate witnesses, investigators say the killing of family members marked a new and brutal turn.