County Executive Douglas M. Duncan (D), who rushed home from a visit to Chicago, said that public schools would be open today.
Across the county, fearful residents and workers stayed indoors, and some streets and public places appeared deserted.
Investigators said that all the victims died where they were shot, in a four-mile-wide cluster just east of Rockville. Two were at service stations -- one buying gas, another vacuuming a minivan. A third was in a supermarket parking lot. A fourth was sitting on a bench outside a post office, and the fifth was mowing grass near a car dealership.
"They're shooting all around!" said a frightened bystander who happened on one of the grisly scenes yesterday morning.
The slayings shattered the fall morning amid the early bustle of the workday, as, one by one, dire reports flashed to police at almost half-hour intervals between 7:41 and 9:58 a.m.
Investigators quickly linked yesterday's four slayings to a fifth Wednesday evening, as well as to a shooting that punctured a store window late Wednesday afternoon, the incident that they believe began the shootings.
The attacks left scenes of horror to be discovered by stunned passersby and morning commuters on a gorgeous morning.
"It was beautiful, it was perfect, it was an ideal morning," said a man who found one of the victims dead in a White Flint parking lot with a gaping gunshot wound to the chest. "That's the part that's strange."
Officials said they believe the shootings began at 5:20 p.m. Wednesday, when someone fired a shot through the window of Michaels, an arts and crafts store, in a shopping center at Georgia Avenue and Aspen Hill Road. The store was busy, but no one was hit.
Assistant Manager Debbie Kay said she heard what sounded like a light bulb pop and then noticed a marble-size hole in the display window and called police.
Forty minutes later and two miles south, 55-year-old James D. Martin was shot while crossing the parking lot of Shoppers Food Warehouse in Wheaton's Glenmont Shopping Center, at Randolph Road and Georgia Avenue.
Martin, who lived in the county's Stonegate neighborhood, north of Colesville, was a program analyst for the National Oceanic and Atmospheric Administration's Office of Marine and Aviation Operation. He was married and had an 11-year-old son.
The shootings resumed yesterday at 7:41 a.m.
James L. "Sonny" Buchanan Jr., 39, who operated a landscaping business, was mowing a strip of grass along Huff Court behind Fitzgerald Auto Mall in White Flint when he was shot once in the torso, according to police and witnesses.
Buchanan had a wound "as wide as a coffee cup," said Richard Tyner, 50, of Germantown, a local office worker who was one of the first to reach him.