Four people were shot to death and three others were wounded in a five-hour period over the weekend, with most of the violence occurring in two areas of Washington targeted for crime prevention after violence earlier this summer.

Mayor Anthony A. Williams (D) and police commanders had visited Southeast Washington and Columbia Heights in Northwest Washington to announce beefed-up patrols after a series of shootings in June that killed a grandmother and injured a mother and her 5-month-old son.

Yesterday, Executive Assistant Chief Terrance W. Gainer said the weekend shootings show that much work remains for the department and in the community. Later yesterday, two more people were shot and wounded in Southeast.

"It is evident that you can't fix long-term crime problems overnight, but we have stayed the course and don't get discouraged by this," Gainer said.

The violence in Columbia Heights early yesterday and late Saturday left two people dead and two others injured.

Police said Levingston Isiah Muir, 24, of Brentwood, was shot multiple times in his head and body in 1300 block of Columbia Road about 10:45 p.m. Saturday. Curious residents stood by as police investigated, later eyeing the circle of dried blood that remained on the pavement yesterday.

"They left his body uncovered for more than two hours," a resident complained.

Hours later, police returned to the neighborhood to investigate the shooting of Kerron "Cam" Pinkney, 20, and two friends.

Police and family members said Pinkney and two male friends were walking to her mother's home in the 1400 block of Monroe Street NW about 2 a.m. yesterday when an unidentified man walked up and shot them. One man was shot in the back and the other was shot in an arm, police said.

Pinkney, of Suitland, was pronounced dead at 11:50 a.m. yesterday.

She was majoring in criminal justice at the University of the District of Columbia and had been mentoring at-risk high school youths, said her aunt, Gail Pinkney. Kerron Pinkney had hoped to follow in the footsteps of her mother, a District probation officer, she said.

"You couldn't have asked for a better person. She had only 29 credits to graduate," Gail Pinkney said.

On the sidewalk where Kerron and her friends were shot, someone had placed three champagne bottles as a tribute.

"She was a good girl," said Darlene Brinkley, who grew up with Kerron Pinkney in the 1400 block of Monroe Street NW and now lives in Prince George's County.

Brinkley acknowledged that community officials and police have said that crime is declining in Columbia Heights, but she said there are still too many people dying. "My brother was killed in an argument over a car in October," she said.

By daybreak yesterday, shootings had claimed the lives of two other District residents, one in Southeast Washington and one in Capitol Heights, just over the District border in Maryland.

Prince George's County police found Southeast resident Jerome Woodard lying in a parking lot in the 4100 block of Southern Avenue, and he was pronounced dead on the scene. Woodard was a resident of the 300 block of 37th Street SE, police said.

About 3 a.m. yesterday, a person driving a damaged burgundy Chevrolet truck opened fire on two men who were standing in the 4700 block of Alabama Avenue SE.

Robert Morris, 29, of the 3300 block of Stanton Road SE, was taken to D.C. General Hospital and was pronounced dead at 3:46 a.m, said Sgt. Joe Gentile, a District police spokesman. A 20-year-old man whom police did not identify was shot in the left leg and foot and was being questioned by police.

"I can tell you that I loved him," Morris's mother, Wanda, said last night. "He's my only child."

She said Robert Morris was a plumber's apprentice and the father of one daughter and two sons.

Several hours later, police reported two more shootings in Southeast, in the 3200 block of Stanton Road. Although those shootings were not far from Morris's residence, police said they had no evidence linking the shootings to the previous violence.

Two 19-year-old men were sitting in a car about 6 p.m. when a group of men approached them and gunfire erupted, police said.

"They were approached by maybe three suspects," Gentile said. "One or more, maybe all three, produced guns and opened fire."

One of the men was shot in the body, and the other was shot in the body and leg. Both men were taken to D.C. General Hospital and were in stable condition last night, officials said.

Investigators did not say whether they knew of a motive, and the shootings remained under investigation last night as police searched for the suspects.

The string of nine shootings in less than 24 hours still did not surpass the numbers on some of the District's bloodiest nights in the late 1980s and early 1990s.

"The problems that cause this type of violence, you can't stop with sheer officers," Gainer said. "What we have to do is focus law enforcement and work on the underlying causes of violence and what leads to murder."

Staff writers Martin Weil and Brian Mooar contributed to this report.