US Park Police said on Twitter that the shooting happened on West Executive Drive this afternoon. District of Columbia Fire and EMS spokesman Doug Buchanan said one patient was taken to a nearby hospital in critical condition shortly after 3pm local time. A DC police spokesman said the Secret Service is investigating. The White House grounds were shut down to pedestrian traffic, locking staff members and reporters indoors. President Barack Obama is not on the premises - he had left two hours earlier for an afternoon round of golf. More to follow