Mourners packed into a church here on Saturday morning, to grieve the loss of Jonathan Sanders and to grapple with the circumstances of his death.

Sanders, 39, died on 8 July, allegedly choked to death by a local police officer in a case state and federal authorities are now investigating. Sanders was black. The officer, Kevin Herrington, is white. Police have appealed for residents to stay calm until the investigation is finished. But at Sanders’s funeral, the grief was mixed with protest.

A thousand people turned out – as many as live in the entire town of Stonewall – and many wore shirts printed with the slogan “Justice For Jonathan”.

“When you put heat to the kettle, the pressure begins,” said speaker Dennis Evans, in remarks that brought the congregation to its feet. “When you turn up the heat, the water starts to boil. And finally when the pressure gets too high, the kettle whistles. That’s us whistling, now, calling for justice for Jonathan.”

Sanders’s mother, Frances, wept in the first pew, as ushers – ladies in white dresses and white gloves – fanned her.

One of those women, Lisa Johnson, 51, is a distant relative of Sanders.

“This is a sad day, Jesus,” she said. “We have a bad history with the police here. Five years ago they beat my cousin to death. Believe and trust me: we have a problem here.”

Stonewall is a small and poor community, about one-third black and two-thirds white. Its landscape is still dominated by the brick hulk of a cotton mill that closed in 2002, leaving more than 800 people jobless.

Everything’s fucked up. My kids are scared to death. That cop didn’t look dangerous. He’s supposed to protect and serve Derek Williams

The Sanders case has gripped Stonewall, where neighbors view their town with a new fear and suspicion. The day before the funeral, Sanders’s 21-year-old cousin, Sierra Sanders, visited the impromptu memorial at the site of his death. As she described to a visitor the events that led to Sanders’s death, a white pickup truck came barreling into sight, skidding to a stop diagonally across the road.

A man, Derek Williams, jumped out of the driver’s seat and said he owned the property on which Sanders died. He demanded to know the visitor’s interest in the case.

“Everything’s fucked up right now. My kids are scared to death,” he said. “That cop didn’t look dangerous either. He’s supposed to protect and serve. And look what happened.”

According to the Sanders family’s attorneys, witnesses to his death give a unified account of what happened that night. At about 10pm Sanders took his horse, Diva, out for exercise. It’s common here to wait until the heat of the day has dissipated before taking horses out.

The body of Jonathan Sanders is displayed at the funeral service in Quitman, Mississippi, on Saturday. Photograph: Chris Todd/The Guardian

Riding in a buggy drawn by the horse and wearing a headlamp on his forehead, witnesses say, Sanders passed a fuel station where a Stonewall policeman, Herrington, was talking to another man. From his buggy, Sanders told the officer to leave the man alone, before continuing on his way.

According to Sanders family attorneys, Herrington said: “I’m going to get that nigger.” He then followed Sanders.

The area is rural and wooded, with twisting roads. Herrington, whose wife was in the patrol car, followed Sanders along several turns in the road, then flicked on his blue lights. The horse, frightened, reared up and threw Sanders from the buggy, then ran.

Sanders, disoriented, climbed to his feet and tried to chase his horse. His headlamp had slipped down around his neck. Herrington made a grab for Sanders, witnesses said, catching him by the headlamp strap around his neck.

What happened next is alleged to have resembled the infamous case of Eric Garner, who was choked to death a year ago by a policeman in Staten Island, New York. Except, witnesses say, it happened in slow motion.

Jonathan Sanders. Photograph: Screengrab

When the pressure gets too high, the kettle whistles. That’s us whistling, now, calling for justice for Jonathan Dennis Evans

Sanders lay face down with his hands beneath him, witnesses told the family lawyers, while Herrington kneeled over him, applying a headlock. They stayed that way for as long as half an hour, waiting for backup and an ambulance. The tableau lasted so long that one witness went home to retrieve an oxygen mask, in case Sanders needed it.

His final words, according to his family’s counsel, were: “I can’t breathe.”

At his funeral on Saturday, the congregation sang the gospel song Break Every Chain. Then various friends and family members in the sanctuary stepped to a microphone to remember Sanders, or to express frustration over his death and the lack of information so far from investigators.

“The slaves waited 246 years, but God delivered them,” said one woman. “I don’t mind waiting.”