PHILADELPHIA (WPVI) -- The Philadelphia District Attorney's Office said Wednesday that the charges for two people accused of fatally shooting a 16-year-old bystander at a Center City SEPTA station have been upgraded to murder.
Tyshaun Welles was shot on January 11 on the westbound SEPTA platform at the 15th Street Station at 15th and Market streets in Center City Philadelphia. He was taken to Thomas Jefferson Hospital in critical condition but later died from his injuries.
Quadir Humphrey, 18, and Zaire Wilson, 16, are now facing charges of murder, conspiracy and other related offenses, the district attorney's office said.
Those charges were upgraded from the original aggravated assault charge following Welles' death.
Investigators believe the deadly shooting stemmed from a disturbance involving a large group of juveniles on the SEPTA platform.
Witnesses said they saw two people, later identified as Humphrey and Wilson, engaging in conversation on the east end of the platform before one of them, believed to be Humphrey, pulled out a gun and fired into the crowd, striking Welles.
SEPTA police said Humphrey is known to police after being arrested two years ago for a weapons offense, as well as last year for unauthorized use of a vehicle.
According to investigators, Humphrey boarded a train from North Philadelphia to go downtown. Once he was at the 15th Street station, he met up with the second suspect.
Shortly after meeting up, Humphrey then fired into a crowd on the platform, shooting the 16-year-old in the head.
Three SEPTA officers were "evidentially visible" on the platform at the time of the shooting, police said.
Investigators found six shell casings at the scene.
"Police found a jacket they believe that the suspect was wearing and wrapped up in the jacket was a semiautomatic handgun, so that is part of the scene," said Philadelphia Police Chief Inspector Scott Small.
Following the shooting, police took the two suspects into custody. Police said the relationship between the three is currently unknown, adding that there is no indication that the victim and the suspects communicated before shots rang out. However, law enforcement is still looking through hundreds of cameras in search of a motive.