NEW ORLEANS — Until he died unexpectedly at his Massachusetts home Jan. 19, Dave Maclellan, 69, devoted much of his retirement to searching the entire state of Louisiana for his son’s killer.

Since his son’s violent death nearly a decade ago in New Orleans, Maclellan made monthly trips to the state with steadfast resolution to identify, apprehend and prosecute the person who demanded money from 38-year-old John Maclellan before shooting him multiple times less than 100 feet from his Lakeview house on July 16, 2004.

John Maclellan succumbed to his wounds and died two month later at Charity Hospital. His family never left his side.

“He was very passionate about the truth, especially when it came to my brother’s murder,” said Dave Maclellan’s son, Michael. Michael Maclellan said he and his siblings will continue the family’s quest for justice.

Michael Maclellan said Dave was an excellent father who taught his four children that you have to earn what you have and not to squander anything. He also said his dad was devoted to U.S. troops serving overseas. When Michael Maclellan served in Afghanistan, he said, his dad sent him a box every week filled with coffee, candy and other luxuries. When Michael Maclellan returned home, he said his dad kept sending weekly boxes to the troops in Afghanistan.

Well known among law enforcement officials in New Orleans, Dave Maclellan was the first to admit that his “pleasant persistence” might be described by some as a “pain in the ass.” But to those who became accustomed to his regular phone calls and visits, Maclellan always acted with gratitude and patience.

Maclellan worked on the theory that someone out there knows something — and the more people he could reach, the better his chances of finding his son’s killer, or finding someone who knew something — anything — about what happened that night.

At first, Maclellan focused his efforts just on New Orleans, handing out fliers at street fairs and festivals, contacting media and meeting with police. As his effort evolved, he began traveling across the state to prisons, detention centers and state penitentiaries to tell his son’s story to inmates.

Maclellan kept in close contact with the New Orleans Police Department detective in charge of his son’s case by phone from Massachusetts on a weekly basis. But he was a strong believer in face time and never let the NOPD forget that he was still around and no less determined to bring justice to his son’s killer.

He also established close relationships with people at the Sheriff’s Office, media outlets, Crime Stoppers and the U.S. Marshall’s Office, as well with people from across the state, including at the Louisiana State Penitentiary, where he regularly attended the Angola Prison Rodeo to talk to hundreds of inmates while they sold their crafts.

Maclellan was known for always bringing gifts, usually in the form of clam chowder, and for his thick Boston accent, which he was well aware made him stick out wherever he went to Louisiana.

“He will be missed,” said Darlene Cusanza, executive director of Crime Stoppers in New Orleans. Cusanza said one of the things she most admired about Maclellan was his eagerness to help anyone he met who had also lost a loved one to violence. He was an advocate for getting all cold cases solved, she said.

“He was special,” Cusanza said. “He was adopted by the community.”

Every time Maclellan was featured in the news, Cusanza said, a few tips would come in, and she would pass them along. But to date nothing that has led to any substantial leads. One of the biggest challenges with the case was Hurricane Katrina, Cusanza said, which drastically changed the neighborhood where John Maclellan was shot. The murder also occurred in an area not known for high crime and without heavy traffic, making witnesses less likely, she said.

Despite the killer still being at large, Maclellan’s persistence achieved small victories along the way. In 2010, his son’s case was put on a deck of Crime Stoppers playing cards featuring 52 unsolved major crimes.

In 2011, an America’s Most Wanted television crew followed Maclellan to Angola and other locations for a seven-minute segment about the murder.

Cusanza said that her organization recommended that Maclellan reach out to those already incarcerated, because when time passes, people are more prone to talk. She said they encourage all families in similar situations to keep the cases of their loved ones visible, a mission Maclellan took to the extreme, but with unwavering optimism and a focus on wanting to ensure that his son’s killer didn’t hurt anyone else.

“Hopefully one day it will pay off,” Cusanza said.

During a visit to New Orleans in October, Maclellan described his motivation: “I can wait for the phone to never ring from the NOPD, or I can come down monthly,” he said. “It’s possible that something may never happen. But it’s also possible something will. I’m taking the approach that it will. I know if I ask enough people, sooner or later good things will happen.”

All families deal with grief and the desire to see justice served differently, Cusanza said, and for Maclellan, “That’s what he needed to do.”

Cusanza said her organization will keep the case open and that John Maclellan’s unsolved murder and his father’s mission will not be forgotten.

“If there’s any comfort,” Cusanza said, “I hope that he’s with his son in heaven and that he has found peace.”

If anyone has information about the murder of John Maclellan early in the morning on July 16, 2004, at the intersection of Belaire Drive and West Harrison Ave., that person is asked to call Crime Stoppers at (504) 822-1111.