It looks like some type of firework went off in this Fresno bus.
What it was... an e-cigarette, similar to this one.
"I guess if they are that dangerous, we should be careful," bus rider Virginia Alvarez said. "Because you could be sitting next to a child."
Authorities say, the man was smoking the cigarette, the driver asked him to put it away.
The man put the device into his pocket.
Then, it exploded.
Adam Wooddy is with Satyr Vapor in Fresno, a shop that sells e-cigarettes.
He says some batteries, like cheap ones bought online or those made for an older type of e-cigarette, are more likely to short, especially if the wrap around it is torn or if the battery touches metal.
"The easiest solution is just keeping a box around it, to keep them in," Wooddy said.
But these explosions have happened before.
New York senator Chuck Shumer even calling for a recall.
"When we see a car has a, when we see several car accidents that might lead to trouble we see recalls," Shumer said. "Why not e-cigarettes?"
Some doctors saying, there's more to learn.
"I don't think that we know everything that we need to know," Chairman of Behavioral Science at MD Anderson Cancer Center Paul Cinciripini said. "But I do think that we can say that less harmful is not harmless."
According to the U.S. Surgeon General, the number of youth and young adults using the devices has gone up 22 percent from last year.
The surgeon general also states the cigarettes are dangerous for brain development.
Wooddy says, the industry is still growing and changing, but he agrees there should be more education, as it does.
"Make sure you're researching, make sure you know what you're doing when you're getting into this," Wooddy said. "Because it could be dangerous."
Part of that change Wooddy says, the newer devices come with technology like safety shutoffs, even chips inside.
Authorities say, the man in the video we showed you was treated for minor burns.
Reporting in Fresno, Megan Rupe.