Hawa Bah, the mother of Mohamed Bah, holds a photo of her late son at a news conference at the New York State Capitol in Albany on April 28. (Tim Roske/Associated Press)

It was early afternoon when Hawa Bah summoned the ambulance. She had arrived the previous day from Guinea on her annual visit to see her son, Mohamed Bah, the favorite of her four children. She found him upset and depressed, but he refused to go to the hospital. So she called 911.

Instead of paramedics, however, police in tactical gear swarmed the red-brick Harlem building where Mohamed Bah lived in apartment 5D. Once inside, they opened fire. When Mohamed was finally loaded into an ambulance that day in September 2012, he was dying from eight gunshot wounds, including one to the head.

The three officers involved in the shooting were quickly cleared by a Manhattan grand jury. But Hawa Bah is now urging authorities to reopen the investigation, joining a flood of families who view this year’s debate over police use of deadly force as an opportunity to demand justice for past shootings.

Buoyed in part by the Black Lives Matter movement, discouraged families that had put down their protest signs are picking them up again, while others are clamoring for vindication from the Justice Department, say civil rights lawyers and police reform advocates.

“We now know that when authorities want to be transparent and efficient with information, they can,” said Daryl D. Parks, a civil rights lawyer who represents relatives of Michael Brown, who was killed by a police officer in Ferguson, Mo., and Corey Jones, who was killed by police in Palm Beach Gardens, Fla. “Most of the families now feel a little bit better, in that justice seems to be a little bit better had.”

On Sept. 25, 2012, Hawa Bah called 911 in New York City, hoping to get medical help for her son Mohamed. Hours later, he was dead after being shot by NYPD officers who came to his apartment. (Gillian Brockell/The Washington Post)

Recently, Hawa Bah and her relatives gathered outside the Justice Department’s New York office, where they were joined by the families of other victims of police violence, including Gwen Carr, the mother of Eric Garner, who died last year after a New York police officer allegedly used an illegal chokehold while arresting him on Staten Island.

“My son’s case has gotten a lot of attention, but other cases, like Mohamed’s, have not,” Carr said. “All the mothers need to stand together to make sure our children get justice.”

A Justice Department official could not confirm the trend, saying the agency lacks “the capacity to statistically analyze” complaints about civil rights violations. Parks and others noted that there’s a high bar for persuading the Justice Department to pursue civil rights charges.

But Bah is hopeful: New information has raised serious questions about the police account of her son’s shooting.

For example, police have long said that they opened fire after Mohamed Bah stabbed officer Edwin Mateo with a 13-inch kitchen knife. But in a recent sworn deposition, Mateo testified that he could not remember being stabbed. Instead, he said, he cried out because he had been shocked by a fellow officer’s stun gun.

Other documents revealed that the knife was never tested for fingerprints and probably never will be: The knife was “contaminated,” police said, when an evidence warehouse was flooded during Hurricane Sandy. And the Bah family’s attorneys say the shot that struck Bah’s head came at a downward trajectory, which they say would be inconsistent to the officers’ claim that he was standing over them with a knife.

The information came to light after Hawa Bah sued the city, saying that the police version of the shooting was, at best, riddled with inconsistencies and, at worst, a coverup.

“It’s clear to us from the inconsistencies in the deposition testimony of these officers that they didn’t have enough time to get their story straight,” said Debra Cohen, a lawyer with the firm Newman Ferrara who is representing the Bah family.

An NYPD spokesman declined to comment, citing the pending litigation. Police declined to provide information about the shooting, including the incident report and the initial news release. Attorneys for the officers involved in the shooting did not respond to requests for comment.

On the day he died, Mohamed Bah was 28, a student at a Manhattan community college and a local cabdriver with no criminal record. His family described him as a loving and compassionate son, who escorted his mother to Ellis Island and the Statue of Liberty each year to celebrate his ability to immigrate legally.

During Hawa Bah’s visit in 2012, however, something felt off. When she tried to coax her son out of his small apartment, he refused and disappeared, barely dressed, into his bedroom. As he slumped into his bed, his mother went outside and called for help.

She first tried two private ambulance services, but the numbers didn’t work. Then she called 911, struggling to communicate in heavily accented English.

Hawa Bah said her son had mental problems, and the dispatcher promised to send an ambulance as soon as possible. Instead, officers from the NYPD’s specialized tactical unit responded, climbing five flights of stairs to the apartment where Mohamed Bah had barricaded himself.

“I said, ‘Please let me talk to Mohamed, he’ll open the door,’ ” recalled the mother, who met the officers outside the apartment building. “They said, ‘No, don’t worry about it.’ ”

What happened next is in dispute. Initially, police said Mohamed Bah opened the door and slashed at the officers as they tried to push him back into the apartment. Stun guns failed to subdue Bah, who tried to stab Mateo. That prompted Mateo to yell: “He’s stabbing me! Shoot him!” And the officers opened fire.

More recently, in sworn depositions, the officers gave a slightly different account: Mohamed was carrying a knife when he opened the door. Four officers pushed him back with tactical shields and tried to subdue him.

One officer fired a bean bag. Another tried a stun gun. A third also pulled his stun gun, aiming it over the shoulders of two other officers.

The wire from that gun struck Mateo, who fell to the ground and cried out in pain, Mateo said under questioning by Hawa Bah’s attorney. That prompted Mateo and two other officers to pull out their guns and start shooting.

“Mr. Bah wasn’t stabbing you while you were on the ground, was he?” the attorney asked.

“No,” Mateo replied.

“When you said, ‘He’s stabbing me. Shoot him,’ did you see Mr. Bah stabbing anybody?” the attorney asked.

“No,” the officer replied.

No matter the circumstance, police are rarely charged with a crime for killing someone while on duty. Of more than 830 fatal shootings this year, seven officers have faced charges.

In November 2013, Manhattan District Attorney Cyrus Vance informed then-NYPD Commissioner Ray Kelly that a grand jury had declined to issue indictments in the Bah shooting, finding that the officers’ “use of deadly physical force was not unlawful.”

Bah’s story soon disappeared from the headlines, and the city moved on. This year, New York police have shot and killed seven people, according to a Washington Post database, tied with San Diego and Oklahoma City for the fourth-highest number of fatal shootings in the nation.

After a spate of protests of police brutality, New York Gov. Andrew M. Cuomo (D) signed an executive order in July requiring a special prosecutor to review all fatal shootings and other deaths at the hands of officers — a move widely praised by activists. But the edict is not retroactive, meaning it will provide no relief for Hawa Bah.

She was there the day Cuomo signed the executive order, invited along with the families of other men who died at the hands of police. While the others wrapped Cuomo in hugs, she offered him only a stiff handshake.

“After I get justice for my son,” she told the governor, “then I will give you a hug.”