Spokesman Pete Piringer says units were dispatched shortly before 6 a.m. to the intersection of Connecticut Avenue and Grand Pre Road for a reported shooting on a Ride-On bus.
Piringer says one adult male victim suffered a "priority one chest wound." A medevac helicopter will be taking the victim to a local trauma center.
Piringer says he's been asked by police not to disclose which hospital.
He says it is his impression that the victim was found on the bus.
This is in the Aspen Hill area of the county.
There is a huge police presence in the area and traffic is affected.
Traffic is completely stopped at Connecticut Avenue in both directions around the scene.
There is no word if the reported shooting has any connection to the sniper shootings in the Washington region.
The shooting occurred around 6 a.m. near the site of five other sniper attacks.