The service was not without controversy. Gwen Carr, Mr. Garner’s mother and Ms. Garner’s grandmother, was turned away from the church. Afterward, Mr. Sharpton said the commotion, including a person who burst into the church yelling during the middle of the service, was part of a “family friction” that should not distract from Ms. Garner’s work.

“I hope we can heal whatever the family friction is and keep fighting for justice,” Mr. Sharpton said after the service.

It was the difficulty of that work — and the fact that it was based on the death of her father — that quite likely took a toll on Ms. Garner, Mr. Sharpton said.

“Her heart was attacked in 2014 when her daddy was choked and begged 11 times for his life and they would never let the grip go,” Mr. Sharpton said. “When she saw the tape of her father, that’s when her heart was broken. Whatever attack came came to the pieces that were left.”

The physiological and psychological effects of battling injustice and racism have become a part of the conversation around Ms. Garner’s death, especially given her recent interview with Benjamin Dixon, host of the podcast “Like It or Not,” during which she said that she was “struggling” with stress and that the “system beats you down to where you can’t win.”

Continuing in the animated tone that was the hallmark of her activism, Ms. Garner described seeing the video of her father’s death.