“I had no idea that my son’s case was closed or that there was a person openly discussing how he killed him,” Katana Dixon wrote in an email to The Post the day after reading about her son’s slaying. (Bill O'Leary/The Washington Post)

For the past 11 years, Katana Dixon has wondered about the night Sean — her youngest child, her baby boy — was gunned down on a quiet street in Northwest Washington.

“It was hard,” Dixon said, flanked by her two surviving children, Michael and Troy. “Grief and pain. They don’t go away.”

Dixon hoped that D.C. police would tell her when they knew something about Sean’s killer. In the days after his Aug. 14, 2001, slaying, investigators spent countless hours sitting in the living room of the family’s home on Rittenhouse Street, paying close attention to those who trickled in and out, perhaps hoping for clues.

“I remember promises: ‘We’ll do everything we can. We’re going to catch this guy,’ ” Michael Dixon, 36, recalled. “But I don’t remember ever hearing from them again.”

The Dixons still haven’t heard from police. But they learned what happened to Sean, who was 22 when he was killed, after his case was featured last month in a series of Washington Post articles about homicides in the District.

In recent years, the District of Columbia has experienced a historic drop in the number of homicides and a concurrent rise in the percentage of cases closed by police.

Khalil Vanterpool, a D.C. man who had occasional run-ins with police, told The Post in an interview that he killed Sean Dixon. Vanterpool said Dixon approached him in the 6800 block of Sixth Street NW to question him about the theft of illegal guns from a car trunk months earlier. He said he drew a .357 magnum from his waistband and shot Dixon in the stomach, leaving Dixon to die on the street while he ran a few blocks to his mother’s house to retrieve his bulletproof vest before going to his girlfriend’s house.

He said he shot Dixon because he thought that Dixon was going to shoot him.

Vanterpool said he met Dixon for the first time at a nightclub earlier that evening. He said the shooting was in self-defense. Police agreed and quietly closed the case in April 2002, eight months after the killing. Police counted it among the successfully closed cases that year, even though they never arrested Vanterpool or even questioned him, according to Vanterpool and police.

Gwendolyn Crump, a spokeswoman for Police Chief Cathy L. Lanier, said in a statement Wednesday that Detective Daniel Whalen made attempts to locate and interview Vanterpool in 2001 and 2002 before ultimately gathering “evidence through other means which indicated Mr. Vanterpool was acting in self defense at the time he shot Mr. Dixon.”

Police called the disposition of the case an “administrative” or “304.1” closure, which occurs for various reasons with no arrest.

“He was a 304.1?” Katana Dixon asked. “What category do you have to be killed in to get the police to care?”

More than 189 homicides in the District have been closed that way since 2000.

This interactive map has details about 2,294 homicides that occurred between 2000 and 2011 in the District of Columbia. Find the killings in your neighborhood, follow the trends over time, and learn how the victims died and what happened to their cases.

“I had no idea that my son’s case was closed or that there was a person openly discussing how he killed him,” Katana Dixon wrote in an e-mail to The Post the day after reading about her son’s slaying. “Was it that easy for you to determine who he was and where he lived? It’s so hard to believe that the police have no interest in pursuing this matter after hearing his statement. So hard.”

Whalen, the lead detective, declined to comment. “I’d love to discuss it with you,” Whalen said. “But unfortunately, I am unable to talk about it. It’s just improper.”

Lanier, who became chief in 2007, said in an interview in September that suspects “cannot be compelled to provide a statement.” Crump, responding for Lanier, said Wednesday that police would not reopen the case unless “sufficient evidence was uncovered or developed which substantially contradicted the evidence upon which the original closure was based.” Crump said police would make an effort to contact Vanterpool.

“I can’t figure out why, when it appeared on the front page of The Washington Post, the mayor didn’t call the police department for some answers,” Katana Dixon said. “It was like Sean never, ever mattered.”

D.C. Mayor Vincent C. Gray (D) did not return a phone call seeking comment.

Police declined numerous requests from The Post to make case records available. Crump said Wednesday those records indicate that a member of the Dixon family was “notified of the results of our investigation.”

Katana Dixon denied receiving police notification and said she doesn’t understand why authorities did not contact the family when they identified the gunman or closed the case.

“I’m angry, upset, hurt,” she said. “I thought if you committed a crime, the police had to bring you in and question you. Apparently, that’s just something on television.”

A life gone wrong

By all accounts, Sean Dixon had a good upbringing. He was the youngest of three boys born to Richard Dixon Jr., a lanky plumber who had served in the Air Force, and Katana, a stunning woman with hazel eyes and an infectious smile who worked for a nonprofit social services agency in the District. The family lived in a brick rowhouse in the 1300 block of Rittenhouse Street NW that had been purchased by Richard’s father, a school counselor, and his wife, a teacher.

Sean Dixon, who was a scrawny 5-foot-10, was a funny and caring kid. He was known to sneak food from the family’s freezer and give it to neighborhood children, his mother said. His parents tried to teach him the importance of community by delivering gift baskets to the needy every Thanksgiving and Christmas Eve.

Dixon, whose mother described him as “gifted and talented” as a young boy, was close to his family until Richard Dixon died of cancer of the esophagus in October 1990. Sean was 12.

During Sean Dixon’s first week in junior high school, a bully gave him a black eye. Sean, who used to talk through problems with his father, didn’t know what to do. So he brought a knife to school to protect himself. And things spiraled downward.

“When Sean was beaten up, he didn’t have his father to talk him through that,” his mother said. “I guess I was so busy . . . that I didn’t see the turn. At some point, he became out there.”

His mother tried to get him into social services programs, but he refused. His older brothers talked to him, but their advice didn’t stick. Dixon began running with the wrong crowd. At the time of his death, he had four felony arrests, but no convictions, according to D.C. Superior Court records.

“We were pretty estranged at the time,” Michael Dixon said. “The path that Sean chose is outside the path of our immediate family.”

The last thing Richard Dixon told his sons before dying was to take care of one another because “that’s all you’ve got,” Michael Dixon said.

‘He didn’t make it’

Sean Dixon wasn’t supposed to die.

See, his brothers, Michael and Troy, had planned to “rough Sean up” when he recovered from the bullet wound. Their plan was to encourage him to turn his life around, to break away from the riffraff he was hanging with.

“Sean was doing some things that we didn’t agree with,” said Troy Dixon, 45, who has two sons. “We had conversations about it.

“I spent the night waiting for him to come out of surgery,” he said. “It was going to be an ‘I told you so’ morning. I couldn’t wait for the morning to come.”

As the brothers waited at Washington Adventist Hospital for news, a doctor emerged. It was near dawn.

“He came and told us he didn’t make it,” recalled Michael Dixon, who had just returned from college in Florida.

Sean died at the hospital where he was born. He was 16 days shy of his 23rd birthday.

Katana Dixon was living in Northern California when Michael called her. He was so shaken that he could barely eke out the words.

“First, you don’t ever think your son’s going to get shot, and then you don’t ever think he’s going to die,” she said. “And I had to fly 3,000 miles alone.”

Katana Dixon, who has moved back to the District, said she has learned to live with the tragedy, but seeing Vanterpool’s picture in the newspaper and reading his version of what happened that night “brought it all back.”

“It makes me feel irresponsible,” she said. “I left it up to the police. I should have pressured them. Maybe then I wouldn’t have had to wait 11 years to find out that it was closed in 2002.

“I still feel as if I’ve had no justice. And I haven’t.”