The incident, which was reported to the California Highway Patrol at 10:47 a.m., occurred on the highway's westbound side just east of Railroad Avenue.
A caller initially told the CHP that two vehicles collided on the highway and that there were gunshots. Responding personnel found just one vehicle at the scene, a black Lexus, according to the CHP.
The Lexus' two occupants, Marie and another man, were transported to John Muir Medical Center in Walnut Creek for treatment of their gunshot wounds. Marie died at the hospital, according to CHP. "The male passenger is in stable," said Pittsburg Police Captain Ron Raman on Wednesday. He said the passenger is expected to survive.
The other vehicle that fled the scene was a newer-model white Mercedes sedan with paper plates, according to CHP. Police said the driver of that vehicle was involved in some type of road-rage incident. No further details on the suspect vehicle were provided.
The incident caused delays on the highway. The three left lanes reopened shortly after 2 p.m., according to the CHP, with all lanes opening up about an hour and a half after that.
The Pittsburg Police Department is leading the investigation and CHP is assisting in the case. While the community of Pittsburg has cameras through the city, there are none along the stretch of Highway 4 where Marie was killed.
“Our chief will be going to the city council on Monday seeking approval to place cameras within our city jurisdiction that monitor Highway 4,” Captain Ron Raman said.
The ages of Marie's children range from 9 months to five years. One of her sons, Ralph, celebrated his second birthday on Thursday without his mother, the day after she was killed.
Marie's mother, Patricia Johnson said from the birthday celebration at her Vallejo home, that Marie was very close to her children.
"She didn't deserve for her life to be taken like this," said Johnson. “I know she’s in a better place,” she added. “She’s not suffering. She’s not in pain.”
The family has no idea who would want to hurt her and said the party was held as a way to keep the kids happy and to ease the pain of their mother's loss.
It's also not the first tragic incident to happen to Marie's children. Family members say the father of one her children was shot and killed in Pittsburg last May.
Marie's brother says the past 24-hours has been hard.
"Everybody is trying to hold on. What could we possibly do right now at a time like this?" said Marvin Washington.
The family is pleading for witnesses or anyone with information to come forward. In the meantime they've set up a gofundme account to help pay for Marie's funeral expenses.
"This is a young lady gunned down like she was nothing. Somebody seen something. Please come forward," said Marie's uncle, Patrick Johnson the day of the shooting.
There have been at least three other shootings on Highway 4 since November and 18 or more across various highways in Alameda and Contra Costa counties in a recent flurry of highway violence.