A teenage boy was fatally shot at a light-rail station in downtown Minneapolis, and police had a "person of interest" in custody within an hour of the shooting.

Officers were called to the light rail platform along 5th Street west of Nicollet Mall at about 5:30 p.m. Tuesday on a report of shots fired, Minneapolis police spokesman Howie Padilla said. First responders tried to save the boy's life, but he died at the scene along the platform.

A single shell casing was found at the scene and police believe the shooter and the victim knew each other. The victim's body lay covered on the platform as police investigated the area.

"This was a conflict of some sort between two individuals who seemed to have known each other," Padilla said. Metro Transit police helped find images of the person of interest to identify him, and a bus operator spotted the person.

This is the 55th homicide in Minneapolis, according to the Star Tribune database.

The entire block where the transit station sits was cordoned off by police, where numerous squad cars and offices were securing the scene.

The incident also disrupted rail service downtown.

By 7:45 p.m. trains resumed through Nicollet Station all the way to Target Field, according to a Metro Transit alert.

A woman getting off the bus on 5th Street moments before described hearing a "pop" as she walked to a nearby store.

"I was like, 'Is that a gunshot?' Yes it was," said Mary Sue, who declined to give her full name. "Scary."

Several dozen bystanders lingered around the yellow crime tape waiting for answers as hundreds of pedestrians bound for the Minnesota Twins game streamed past the scene.