Robert Barnes' death is a tale of terrible consequences that started, according to police, with a thoughtless lie a 10-year-old boy told his mother to explain why he was late getting home.

The boy said a homeless man had hit him at the Olney Sunoco station where both were offering to pump gas for spare change. The boy's mother and two other women allegedly responded by packing three adolescents into a minivan and going to the gas station to exact revenge. A surveillance camera captured the assailants bursting from the vehicle and beating the homeless man with a hammer and a chair leg. Barnes stopped moving soon after they began, but the beating continued.

Soon after the April attack, Barnes slipped into a coma from which he never recovered. His death last week was ruled a homicide.

Despite the surveillance video and the coroner's ruling, Philadelphia District Attorney Seth Williams has yet to charge the adults implicated with murder. They remain in jail on assault and attempted murder charges, having rejected an earlier plea bargain that would have given them seven to 14 years.

Upgrading the charges should be an easy call - in contrast to Williams predecessor Lynne Abraham's wrongheaded decision to rearrest and file a murder charge against a man who shot a police officer 40 years before he died. In a bizarre coincidence, the accused in that case was William Barnes - Robert Barnes' uncle, according to Newsworks.

Robert Barnes' fate is not as rare as it should be. The National Coalition for the Homeless says there are about 97 violent attacks on homeless people each year, about 25 of them fatal, and that many more likely go unreported. The surveillance video of Barnes' savage beating shows why: Some view the homeless as less than human.

But Barnes, 51, was human. His sister, Diane Barnes, told The Inquirer that he grew up in Roxborough, attended Catholic school, and worked as a roofer with his father. But he drifted into alcoholism and spent the last 20 years of his life on the streets. He refused family offers of shelter because they came with a requirement that he get sober.

Barnes' sister has set up a GoFundMe account to cover his funeral expenses. Excess funds will go to help other homeless people. The advocacy group Project HOME helped make arrangements for Barnes' service being held Saturday.

Strangely, Barnes' assailants may have put themselves on a path to the troubles he endured. Nationally, about 20 percent of ex-convicts are homeless, partly because they have trouble getting jobs, housing, and credit. The problem is worse in cities: The California Department of Corrections reports that as many as half of urban parolees are homeless.

Regardless of wealth or status, people deserve justice. The district attorney should press the appropriate charges and show that Philadelphia won't tolerate attacks on its most helpless.