A jury convicted a 15-year-old boy of first-degree murder Wednesday in the 2009 beating death of a Chicago high school honor student that was captured on video and seen around the world.
As the verdict was read, the accused teen's family members ran out of the courtroom yelling "Oh lord, Oh lord."
The teen fell back in his chair and shook his head.
During the two-day trial, prosecutors contended that the then-14-year-old high school freshman was part of the mob that pummeled Derrion Albert with fists and feet, stomped on his head and struck him on the back of the head with a board, killing him.
The boy, who is not being identified because he is a juvenile, is among five people charged with murder in the case.
Prosecutors argued that the youth — who landed a single punch on Albert's face — worked with others to kill Albert.
"The defendant, with that punch, signed Derrion Albert's death certificate," said Assistant State's Attorney Matthew Howroyd.
Prosecutors said the youth's punch was thrown so hard that Albert wasn't even able to put his hands up to break his fall. That, they argued, set in motion Albert's death
The defendant "put Derrion in a position he could never recover from," Howroyd said.
Key testimony came earlier Wednesday from a pathologist who conducted the autopsy, who testified that the boy's punch contributed to Albert's death.
"Yes, I believe that punch was a contributing factor to his death," said Dr. Hilary McElligot.
She added that it was impossible to tell which of the many blows killed him, but they all contributed to his death.
Defense attorney Richard Kloak had acknowledged that his client punched Albert as he staggered to his feet after being knocked on the head with a long board. But Kloak insisted that "his act did not cause the death."
"He didn't stomp anybody, hit anyone with a stick or hit anyone on the ground," Kloak argued. "He may be guilty of something else (but) he is not guilty of first-degree murder."
Albert's beating was captured on cell phone video and shown around the United States, providing the most vivid example of the escalating violence that in a six-month period claimed the lives of more than 20 Chicago public school students.
His death prompted President Barack Obama to send U.S. Attorney Eric Holder and Education Secretary Arne Duncan to the city.
The sentencing date for the teenager is Jan. 18.