Chicago ? Cell phone footage showing a group of teens viciously kicking and striking a 16-year-old honors student with splintered railroad ties has ramped up pressure on Chicago officials to address chronic violence that has led to dozens of deaths of city teens each year.

The graphic video of the melee emerged on local news stations over the weekend, showing the fatal beating of Derrion Albert, a sophomore honor roll student at Christian Fenger Academy High School. His death was the latest addition to a rising toll: More than 30 students were killed last school year, and the city could exceed that number this year.

Prosecutors charged four teenagers Monday with fatally beating Albert, who was walking to a bus stop when he got caught up in the mob street fighting, authorities said.

The violence stemmed from a shooting early Thursday morning involving two groups of students from different neighborhoods, said Tandra Simonton, a spokeswoman for the Cook County prosecutor’s office. When school ended, members of the groups began fighting near the Agape Community Center.