A security guard was fatally shot in the District on Tuesday during a violent day in which several other people, including two children, were wounded by gunfire, police said.

The female guard, who was working as a special police officer, was shot about 8:30 p.m. in the 3300 block of 10th Street SE, said Police Chief Robert J. Contee III. He said she was on duty in the area of the shooting but gave no indication of the circumstances of the shooting.

Hours earlier, a 9-year-old boy was grazed by a bullet and a man was seriously wounded in Southeast Washington, police said. Police said Tuesday evening that the man was in surgery and his condition was not immediately clear.

And on Tuesday morning, five people, including a 13-year-old boy, were shot and wounded while standing outside a convenience store on Alabama Avenue, also in Southeast. The victims in that incident appeared to have suffered injuries not considered life-threatening.

The violence added to the frustration for Contee as he confronts a steady stream of shootings and a growing number of homicides midway through his ninth month at the helm.

Homicides in the District are up 13 percent over this time last year, which ended with a 16-year high.

Addressing the 8:40 a.m. shooting outside a strip of stores on Alabama Avenue, Contee noted the mayor’s Building Blocks DC initiative, which concentrates resources on the 2 percent of city blocks where more than 40 percent of shootings occur, as well as other programs that emphasize a public health approach to fighting crime.

But Contee also said some criminals simply need to be removed from public life.

“You can’t program your way out of some things; you can’t police your way out of them,” the chief said as detectives and crime scene technicians scoured the parking lot behind him for evidence. “You’ve got to hold people accountable, who are not ready to be in community, when they come out and commit these brazen acts.”

Contee, whose force is down about 200 officers from last year, said he understands that many people need help, but he also said shootings such as the one at the shopping center are “unacceptable behavior . . . and shouldn’t be tolerated by anyone in this community.”

Hours earlier, about 12:30 a.m., police had responded to another shooting, this one in the Trinidad neighborhood in Northeast Washington near Gallaudet University, that left a man dead. Three people were fatally shot Saturday, two men in one incident in Southeast and a 17-year-old in Northwest.

The 8:40 a.m. shooting occurred in the 2200 block of Alabama Avenue SE in a parking lot for a convenience store, a discount shop and a business selling mobile phones.

Early in the investigation, police had not determined a motive and knew of no suspects, and could not say who, if anyone, might have been targeted. Contee described a “lone gunman” wearing blue jeans and standing on 22nd Street firing toward the group at the other end of the parking lot. Authorities said one man and two women were wounded and were taken by ambulance to hospitals. Two others who were wounded, including the 13-year-old, sought treatment on their own.

Arline Mobley, a 62-year-old mother of eight and grandmother of nine who lives nearby, paused at the crime scene. Don’t cut back on police, she warned, while also saying that locking people up isn’t the answer.

“There are people who need help, who actually need help,” said Mobley, who lost one of her sons, 20-year-old Nadar Mobley, to gun violence in the District in 2010 in a case that remains unsolved. “There are so many people who need help, it’s pathetic. And they don’t know where to get the help from. They don’t know about programs and this or that, because nobody comes looking for them.”

The Tuesday afternoon shooting occurred about 4:45 p.m. in the 1500 block of Morris Road SE. Police said a preliminary investigation showed at least one shooter intervened in a dispute between two 9-year-olds. One of the children, along with a man in his 30s, was shot, police said. They were searching for two teens.

Several other victims this year have been children. In July, 6-year-old Nyiah Courtney was killed by a stray bullet as she walked with her parents, who also were wounded, along a street in Southeast. In August, a 2-year-old boy and his mother were apparently caught in crossfire and wounded while inside a vehicle in Anacostia. Earlier this month, a 12-year-old boy was shot and wounded in the LeDroit Park area.

Assistant D.C. Police Chief Andre Wright, who oversees three patrol districts, including the 7th District where both of Tuesday’s shootings occurred, had the morning off. But he sped to the Alabama Avenue shopping center dressed in street clothes.

Wright noted the crime scene behind him, quiet but for police, passing motorists pausing only for stoplights, and a few others.

“All the residents who know about this or who are in earshot of this should be here,” Wright said. “They should be here in disgust. They should be here in anger. Too many times, it’s just the police, a few concerned citizens, a few activists, and then after 24 hours, everyone leaves, and it’s never resolved.”

Fixing the crime problem, Wright said, is “going to take more than what the Metropolitan Police Department can do.”

Dana Hedgpeth contributed to this report.