Virginia police officers acted unlawfully when ordering two BBC journalists to delete images from their cameras after Wednesday's on-air shootings near Roanoke, the attorney for a photojournalism group alleged Thursday.

In a letter addressed to a spokesperson for Virginia State Police, Mickey Osterreicher, general counsel National Press Photographers Association, calls the forcible deletion "unlawful" and calls on the agency to investigate the matter.

"The NPPA is extremely troubled by what appears to an attempt to prevent them from covering the story or document police activity," Osterreicher writes. "For us this is the worst example of a prior restraint of free speech and of the press. While I understand tensions were high this misguided and illegal action was an abridgment of the First, Fourth and Fourteenth Amendment."

Osterreicher's letter comes less than a day after BBC journalists Franz Strasser and Tara McKelvey were asked by Virginia police to delete images from their cameras taken while covering the story of the murders of Alison Parker and Adam Ward, two journalists from CBS affiliate WDBJ in Roanoke, Virginia.

Strasser and McKelvey arrived near the scene where Vester Flanagan, the suspected shooter, fatally shot himself and were ordered by police to delete their images or risk having their cameras confiscated and their car towed.

McKelvey said he elected to delete the images rather than hand over his camera, which would have jeopardized his ability to continue reporting:

The Virginia State Police are looking into the forcible deletion and say that such an order would violate stated policy:

The circumstances of the incident — journalists being threatened while covering the shooting of two other journalists — is especially vexing, Osterreicher writes.

"The chilling of these rights would be bad enough, but occurring as part of the coverage of the tragic death of journalists doing their jobs makes it even more disconcerting," he wrote.