The arrest of Tristan Fisher, 18, was announced Wednesday afternoon by the Delaware County District Attorney's office.
The shooting happened just before 4:00 p.m. Tuesday in the unit block of Lexington Avenue.
Authorities say Kamara got into a fistfight on Lexington Avenue, and got the best of his opponent who police have not identified. Fisher told police it was his cousin, but won't reveal the name. Police believe he may go by the name Devon.
However, police believe that fight led to Fisher shooting Kamara, killing him.
"Fischer told police Kamara began to approach him and he, Fisher, picked up a gun on the sidewalk and shot Mr. Kamara three times," said District Attorney Mike Green.
Kamara's sister called her brother moments before he was killed and listened as the chaos unfolded.
"I just heard him crying and screaming. I'm like, 'Mohammed, what's wrong, what's wrong?" said Aisha Kamara. "The phone got disconnected, I called back and then I heard 'Who shot him? Who shot him?"
Kamara was taken to hospital and pronounced dead on arrival.
Investigators still don't know what instigated the fight. Fisher is from Northeast Philadelphia and it's unclear why he was in Lansdowne.
Kamara was a senior at Penn Wood High School, who dreamed of a career in business. Relatives say he had several sholarship offers for academics including one to Wesley College in Delaware.
His mother was in tears while trying to talk about the shooting that took her son's life.
"I don't know, I wish someone would explain to me," Fatmata Danjaji. "All I need is my son, all I need is my son."
Anyone with information is asked to call East Lansdowne Police at 610-259-2308 or the Delaware County Criminal Investigation Division at 610-891-4700.
