Griffin was a 2012 graduate of Sherwood High School, where he played football.
The attack appeared to be one of the most violent to occur inside the Metro system in many years. It also focused attention on the troubling problem of street robberies in the city.
Police said that nine youths, ranging in age from 15 to 17, were arrested. One of them, a 17-year-old male, was charged with second-degree murder while armed, police said.
Authorities said another of the youths was charged with aggravated assault and robbery. The others were charged with aggravated assault.
A second person was apparently injured in the dispute and taken to a hospital in stable condition, police said.
After the robbery on Columbia Road, Griffin and “other individuals” went to the Metro station, which is less than a mile away in the 2700 block of Connecticut Avenue, near the National Zoo. The station serves Adams Morgan and the zoo.
Inside, police said, Griffin and the others encountered the robbers. After the attack on Griffin was reported, D.C. police and Metro transit police quickly detained nine people, police said.
It was unclear what was taken in the robbery or where in the station the stabbing occurred.
But one man who went into the station shortly after the attack said he saw a woman trying to resuscitate someone who was on the floor just outside the station’s fare gates.
On the platform, at a lower level, the man said that within minutes, police were handcuffing several young men and telling them to sit on the ground.
“It was clearly tense,” the man said. He described a search of the tracks by police, apparently for possible weapons.
One police official said “several weapons” were found on or near the platform.
One account circulating among friends of Griffin’s was that he may have been robbed of a name-brand jacket, but that could not be confirmed.
“It’s such a tragedy,” said William M. Gregory, the principal of Sherwood, a school of about 2,100 students on Olney Sandy Spring Road in the northeastern part of Montgomery. “This is all such a shock.”
Gregory called Griffin “a real nice kid” who was hardworking and “a great football player.”
The principal said that Griffin “cared about the school, his family, the people inside the school.” He was “dedicated to Sherwood,” a school oriented toward its neighborhood and community, Gregory said.
Michael Miehl, who taught Griffin in chemistry class, said he was “a good young man.” Miehl described Griffin as a student who was respectful and showed an interest in the subject. “He enjoyed our labs and demos,” Miehl said.
Friends and neighbors mourned Griffin’s loss.
One neighbor in Olney described him as constantly friendly and polite, and the son of a hard-working woman.
The neighbor happened to encounter him Friday afternoon
“I saw him,” said the woman, who did not wish to be identified by name. “He was so jovial,” she said, recounting his greeting, “ ‘ Hi . . . How’re you doing?’ ”
She had no way of knowing, she said that it would be the last time they would meet.
Matt Zapotosky contributed to this report.