The grainy black-and-white photo shows the aftermath of a violent encounter: a group of onlookers, many of them African-American, stand around the body of a black man lying on the pavement beside a fire hydrant. 

Next to the man is a defiant-looking 21-year-old, a military veteran in a flat cap, squatting with his elbows on his knees. He is the dead man's son.

The photo was taken 70 years ago, in late February 1948, at the end of a fatal confrontation between Gretna policeman Alvin Bladsacker and 44-year-old Royal Cyril Brooks, a local workman, over a nickel. 

A few minutes before his death, Brooks had been waiting to board a bus at the Gretna ferry terminal. A white woman in front of him in line paid her nickel fare but then realized she had boarded the wrong bus. She asked for her nickel back, but the bus driver refused. Brooks, waiting behind the woman, offered to ride on her fare and handed the woman his nickel.

For reasons that remain unclear, this infuriated the driver, who kicked Brooks off the bus and called over Bladsacker, who was directing traffic nearby. After some sort of altercation, Bladsacker fired two rounds into Brooks' stomach, fatally wounding him, according to an account at the time in The Louisiana Weekly, an African-American newspaper.

Weekly photographer Marion Porter snapped the photo of the crowd gathered around Brooks' lifeless body.

Largely because of the photo and the ensuing publicity, Bladsacker was indicted and eventually tried for manslaughter. He was acquitted after a brief jury deliberation, according to British historian Alvin Fairclough's book "Race and Democracy: The Civil Rights Struggle in Louisiana, 1915-1972." 

Brooks' grandson, Roy, wasn't born until eight years later, but he grew up in the shadow of the incident. 

"I used to see that guy when I would go down to the terminal," he said, referring to Bladsacker. "It was really difficult."

Roy Brooks and his relatives may get some sense of closure this weekend, when a commemoration ceremony is held at Mount Pilgrim Baptist Church in Harvey. Gretna Mayor Belinda Constant will speak, and Parish President Mike Yenni is sending a representative. Several descendants of Royal Brooks will attend as well, including several from Wisconsin. 

Ira Melita Brooks, Roy's sister, is looking forward to the ceremony. "It's really an honor," she said. "He left a great legacy."

The commemoration is the outgrowth of an effort by the Civil Rights & Restorative Justice Project at Northeastern University's School of Law, which is aimed at investigating "the role of state, local and federal law enforcement agencies and courts in protecting activists and their work."

Kaylie Simon, an attorney with the project, said the case never would have drawn attention except for its mention in Fairclough's book. A law student was assigned the case and began piecing the full story together using public records, Simon said.

Brooks' death did have an impact. The publicity that followed, which led to Bladsacker's indictment, prompted the formation of the Louisiana branch of the Civil Rights Congress, a civil rights legal group based in New York. 

The commemoration aims to celebrate that development, but also to remember Brooks himself, a snappy dresser and regular churchgoer who worked the gate at the "colored" section at local minor-league baseball games, his grandson said. 

"He was a guy that got along with everyone," he said. 

Royal Brooks' wife died in childbirth, Ira Melita Brooks said, leaving him to raise his children on his own. "He took care of his family," she said. 

Other details about her grandfather's life are scant, she said. Her father, the young man in the Louisiana Weekly's picture, was deeply scarred by the incident: His father died in his arms.

"He didn't speak about it at all because it really hurt him," she said. 

Constant, Gretna's mayor, is preparing a proclamation for the event. "I'm sorry they had to endure such injustices," she said.

Gretna is a better place today, she said. "I'm grateful for change and that we live in a time where our focus is on inclusiveness and a community that treats all people equally," she said.

The Gretna Police Department won't be represented at the commemoration. Chief Arthur Lawson said he had not heard of the event and couldn't comment on what happened 70 years ago. 

Roy and Ira Melita Brooks said that while some things have gotten better, the city is not perfect.

"There's progress being made, but we still have a ways to go," Ira Melita Brooks said.

Roy Brooks said he still worries when he drives or walks the streets of Gretna late at night.

"Gretna's at a standstill," he said. "I don't feel it's welcoming for me."

But both Roy and Ira said they resist feeling angry, choosing instead to focus on what they've learned about their grandfather. 

"Now we know the whole story and we feel as if we know our grandfather," Ira Melita Brooks said. "He was a man of integrity. He was killed while doing the right thing."

Follow Faimon A. Roberts III on Twitter, @faimon.