Tinesha Julien of Somerville had big plans for her 23d birthday bash on July 3. She wanted to dance away the evening to Caribbean soca at a Quincy nightclub, wearing a new cream-colored dress with a bright red belt and shiny red pumps.

At the home of her friend Tamika Lewis last week, she modeled the dress.

“She had already printed out all the fliers,” said Lewis, 32. “She was so excited.”

Julien, 22, was killed in a hit-and-run accident in Hyde Park early Saturday. Police are still searching for the driver, who they believe was operating a black four-door Jeep Liberty.

“We continue to ask community members who may have information related to the accident to help us in the investigation,” said a Boston police spokesman, Officer James Kenneally.

Tinesha Julien.

‘She wanted to do something to help people.’

Relatives say they still cannot believe that the young woman with the sunny temperament could have been the victim of such a tragedy — and they are devastated for her 2-year-old son, Alijah.

“Right now, I’m numb,” said Avonda Julien, Julien’s mother, at the family’s home in Somerville. “I feel like some person just opened up my head and my stomach and took everything out. It’s like an empty feeling.”

Tinesha Julien’s aunt said she was “at a loss for words.”

“You just can’t come to grips with it,” said Miriam Bartlett.

Julien was struck about 4:45 a.m. Saturday at the intersection of River and Rosa streets, police said. She had left a party in the Fenway with her boyfriend, Kevin Lewis, who is Alijah’s father and Tamika Lewis’s brother.

Julien dropped him off at his Hyde Park home, parking across the street and walking him to the door to say goodbye. As Julien walked back to her car, Lewis said, she was struck by the vehicle.

The driver did not stop to help her, he said.

Kevin Lewis, 28, was inside his house when he heard the accident, then Julien’s shouts for help.

“I didn’t see anything — I just heard it, and I ran right to her,” Lewis said.

Julien had suffered head trauma and was taken by paramedics to Boston Medical Center, where she was later pronounced dead, police said.

Police have obtained video from a nearby surveillance camera, and they believe the black Jeep Liberty that struck Julien has a black wheel cover with red and blue lettering. It was last seen traveling southwest on River Street toward Cleary Square.

Avonda Julien said she hopes that the person responsible surrenders or is turned in by someone who knows what happened.

“I hope we get justice,” the mother said.

At the site where Julien was struck, candles sat on the curb in front of a stuffed panda holding a heart that read “Best Mom.”

“She did everything that a good mother is supposed to do — taking care and providing by any means necessary,” Kevin Lewis said.

Friends and family knew her as a friendly woman with a ready smile who loved movies, watching sports, and outings at the beach. She was committed to her family and cherished spending time with small children, often offering to baby-sit for relatives.

“Even from the time she was a little girl, she would always pass and say ‘Hi’ to everyone, always smiling and taking people under her wing,” Avonda Julien said.

Julien had bubbled with enthusiasm when she learned that Tamika Lewis was pregnant, excited to think that their two children would grow up as friends.

Julien graduated from a medical assistant program at the Everest Institute in Chelsea this year.

“She wanted to do something to help people,” Kevin Lewis said.

She had worked in a doctor’s office in the past, her mother said, and was excited about the prospecting of landing a new job.

“She never liked to stay idle,” Avonda Julien said. “She just wanted to work.”

Bartlett said they have not told Julien’s son about what happened, but it is clear that the toddler knows something is wrong, she said.

He calls out for his mother again and again.

“He can’t say that he misses her,” Bartlett said, “but we know that he misses her.”