When Hassan Sharif first stepped inside the Charlie Dew Drop Boxing Club in Newark, New Jersey, he was a young dad with a hulking frame. But what stood out more than his size, his former boxing coach said, was the quiet, dignified way he carried himself outside of the ring.

“He was all muscle,” said John “Brother Yahya” Thompson, who trained Sharif for a handful of amateur bouts in the late 1990s. “But he was a peaceful guy. I’ve never even heard him argue.”

Sharif went on to become the imam of one of Newark’s most storied mosques. He developed a reputation as a tireless community leader who fed the needy and fought gun violence.

But Sharif, 52, was fatally shot outside the Masjid Muhammad mosque on Jan. 3, a still-unsolved murder that has stunned and baffled those who knew him well.

“When I heard what happened, I was like, ‘Who’d want to do something to him?’” Thompson said.

Newark detectives are investigating whether a family member is behind the killing, three law enforcement sources have told NBC News. It wasn’t clear what may have motivated the attack.

A spokesperson for the Essex County Prosecutor’s Office, which is leading the investigation, said it remains ongoing. He declined to comment further.

The revelation that the killing may have been carried out by a relative came as a shock to some of Sharif’s close friends and family.

“If it was somebody in the street world, I could understand that, because he was trying to put a stop to the crime around the neighborhood,” his cousin Andre Little said. “But for the life of me, I couldn’t even begin to understand why somebody in his family would want to hurt him.”

“Whoever did this,” Little added, “they’re not safe anywhere they go.”

The incident wasn’t the first time an imam who led the mosque was killed. It also wasn’t the first time that someone had pulled a gun on Sharif outside his house of worship.

‘He always showed up for us’

Sharif was raised in Newark, where his father ran a tire repair shop. His given name was Tony Wooten. But he changed it after converting to Islam around the age of 20, his cousin said.

Sharif became imam of Masjid Muhammad in late 2018 when he was 47 and already working as an officer for the Transportation Security Administration at Newark Liberty International Airport. His relative youth allowed him to connect with young people in a way that many imams cannot, his supporters said, and he quickly became known as a progressive leader for whom no request was too big or small.

Sharif gave lectures at local high schools, attended rallies on climate change and police brutality, participated in interfaith events for murder victims, and went out into the streets to implore gang members to turn their lives around.

“Any rally, any community event, the imam was always on speed dial and he always showed up for us,” said Dawn Haynes, a Newark Board of Education vice president and member of the mosque.

Four weeks before Sharif was killed, Haynes’ 11-year-old daughter was raising money ahead of a cheerleading competition in Florida. He welcomed her into the mosque to make her pitch.

“The imam didn’t hesitate,” Haynes said, “and he made sure other congregants supported her, too.”

Sharif volunteered at a local food pantry. He also opened up his mosque for the Muslim League of Voters to serve hot meals to people in the community.

Jimmy Small, the organization’s president, said Sharif had a great sense of humor and the ability to connect with people from all different walks of life.

“On the days he did the feedings, cops would come up to have friendly conversations,” Small said. “Drug addicts, alcoholics, all kinds of folks — they would all come and talk to him.”

Newark Mayor Ras Baraka said he last saw Sharif at an event held at a local church to provide support to family members who were grieving the loss of friends and relatives.

“The imam spoke in church to many people praying for their families who lost loved ones during the past year, not knowing his life would soon come to an end,” Baraka said at a gathering of Muslim leaders last week.

“He was in service all the way up to his last days.”

On Jan. 3, Sharif arrived at the mosque for morning prayers in the pre-dawn hours. He was still inside his car when he was shot multiple times at about 6:15 a.m., authorities said. The imam was rushed to a nearby hospital, but he couldn’t be saved. He died at 2:20 p.m.

As the news spread across the city and state, dozens of worshipers and friends of Sharif’s gathered at the mosque, a former vaudeville theater painted in a distinctive teal and yellow.