A GoFundMe page set up to raise funds for the boys' families identifies them only as Kevin and Sean. Kevin is the younger boy.
"Why us? Why them?" the GoFundMe page reads. "They were only 11 and 14. They didn't get the chance to see life ahead of them, because some cruel people don't have hearts."
The children were the city's first and second homicide victims of 2019, CBS San Francisco reported. No suspects have been identified in the case, authorities said.
Detectives believe the boys were sitting in the van when they were confronted by an unidentified shooter or shooters, who fired multiple rounds into the vehicle, according to authorities. Union City police Lt.Steve Mendez told the CBS affiliate it is possible the boys went to the school to meet up with someone because it is a relatively secluded location.
It is not clear if one of the boys was driving the van or if a third person was inside and fled following the shooting.
"The Union City Police Department is diligently looking into the motive for this tragic incident," a news release issued by the department stated. "At this time, the department has not ruled out the possibility that the incident was gang-related, but that possibility is currently unverified.
“Crime scene investigators have collected several items of evidence, including shell casings. The investigation is ongoing, and the department cannot provide a description of the weapons used, the caliber or number of weapons involved.”
Neighbors of the school reported hearing between 15 and 20 gunshots. A security camera video The Mercury News obtained from a nearby home appears to show headlights, presumably from the van, moving through the parking lot.
A moment later, several bright flashes, believed to be muzzle flashes from one or more weapons, light up the darkness. The van initially appears to speed up in flight, but then comes to a stop.
At least one apparent gunman can be seen running away on foot and getting into another vehicle, which appears to speed off.
"All of a sudden, we heard this pop, pop, pop, pop, I mean it just kept going. It almost sounded like a machine gun type; I mean it was just constant," Gigi Erickson, who lives near the school, told CBS San Francisco.
Police officials released a photo of the parking lot later in the morning that shows about 30 yellow evidence markers on the ground, though the photo is not clear enough to see if they mark shell casings or other evidence.
Below, watch the video reportedly obtained from a security camera near the school, courtesy of The Mercury News.
Like investigators, Erickson wondered why the children were in the parking lot at that hour of the morning.
"I'm just so heartbroken that these kids had to go through that," she told the news station.
The younger boy's brother, Sebastian Melgoza, told the San Francisco Chronicle Sunday that he last saw his brother three days before the shooting. He said he was uncertain who was driving the van or why his brother was in the parking lot.
"Nothing to do? Bored?" he guessed, according to the Chronicle.
A post on the New Haven Unified School District's Facebook page said one victim was a student at Itliong-Vera Cruz Middle School. That post has since been deleted, but a district spokesman confirmed to the News that the information was accurate.
A new post on the district’s Facebook page said only that one victim was a current student in the district and the other was a former student.
"We will have support for our students and staff at the sites where these students attended when school resumes after the Thanksgiving break," Superintendent John Thompson said in the post. "We also work closely with the Union City Police Department to ensure that our schools are as safe as they can be."
Family, friends and neighbors of the two boys gathered at the elementary school Sunday, creating a makeshift memorial for the slain children and holding a vigil in their honor. The News reported that, as mourners gathered and laid down flowers and candles, broken glass from the van's windows still littered the pavement.
"Both of them were such a young age," Shirley Sedano, a family member of one of the victims, told the News. "What can an 11- and 14-year-old do to somebody so bad to have 15 to 20 bullet holes in a van? "If they're trying to get back at somebody, why target the kids? They're just starting to live their life."
A man who identified himself to the Chronicle only as the father of the older boy, Sean, sat on a curb with his head in his hand, the newspaper reported. He sat that way for more than an hour, moving only to adjust a sign memorializing the slain boys.
Frances Michel Lucero, a resident of the usually quiet neighborhood where the boys died, knelt and prayed at the memorial for the children, the News reported. She called the shooting a tragedy.
"It's so senseless for children to just be murdered. I don't know what the circumstances were, but this is terrible," Lucero said.
Union City Councilman Jaime Patiño said the vigil was an important step for healing in the community.
"There will be other memorials for the kids and their families, but right now the community needs to heal," Patiño told the News. "This is something that just doesn't happen. And so, it was very important that we get together as soon as possible and get the community together."
Patiño told the newspaper the circumstances that brought the boys to the site of the shooting, whether good or bad, are not as important as the grief their loved ones are feeling.
"They were somebody's children," the councilman said.
Union City police detectives are trying to determine if there is a connection between Saturday’s double homicide and a nonfatal double shooting that took place three days earlier and a half-mile away from where the boys were killed.
In that incident, two men were shot around 12:30 a.m. near 8th Street and C Street, police said in the news release. The men were taken to a hospital, where they were treated and released.
"Although there is no evidence to show that these two incidents are linked, investigators have not ruled out that possibility," the release said.
Anyone with information on the shootings is asked to contact the Union City Police Department via its anonymous tip line at 510-675-5207 or via email at firstname.lastname@example.org. Information can also be submitted to Detective Joshua Clubb at 510-675-5227 or via email at email@example.com.