Here is a timeline of the shootings so far.

All times are in Washington DC, USA time

1: 5.20pm Wednesday 2 October
Shooting at Michael's craft store in the Aspen Hill area. Windows shattered, but no-one hurt.

2: 6.04pm Wednesday 2 October
James D Martin, 55, of Silver Spring is killed in a grocery store car park in Wheaton.

3: 7.41am Thursday 3 October
James "Sonny" Buchanan, 39, from Arlington, Virginia, is killed while cutting grass at a car dealership in the White Flint area.

4: 8.12am Thursday 3 October
Prenkumar Walekar, 54, a taxi driver from Olney is killed as he filled up with petrol at a station in the Aspen Hill area.

5: 8.37am Thursday 3 October
Sarah Ramos, 34, from Silver Spring is killed outside a post office in Silver Spring.

6: 9.58am Thursday 3 October
Lori Ann Lewis-Rivera, 25, from Silver Spring is killed as she vacuums her van at a petrol station in Kensington.

7: 9.15pm Thursday 3 October
Pascal Charlot, 72, from Washington, DC is killed while walking on a city street.

8: 2.30pm Friday 4 October
A woman is wounded when she is shot in the back in the car park of a shopping mall in Fredericksburg, Virginia, about 80 kilometres (50 miles) south of Washington.

9: 8.00am Monday 7 October
A 13-year-old schoolboy is shot and seriously hurt while being dropped off at Benjamin Tasker Middle School in Prince George County in the Maryland suburbs of the US capital.

10: 8.15pm Wednesday 9 October
A man is shot dead at a petrol station just after filling his car in the Virginia town of Manassas, 48 kilometres (30 miles) southwest of Washington

11: 9.30am Friday 11 October
Kenneth Bridges is shot dead at a petrol station near Fredericksburg, in Virginia, 60 kilometres (40 miles) south of Washington DC.

12: 9.15pm Monday 14 October
Linda Franklin, 47, is shot dead as she and her husband load their car outside a store at the Seven Corners Shopping Center, one of northern Virginia's busiest junctions.

13: Shortly before 8.00pm Saturday 19 October
A man is shot once in the stomach as he leaves the Ponderosa diner with his wife in Ashland, 110 kilometres (70 miles) south of Washington. He is very ill, but expected to survive.