"We saw it hit, the tail broke off almost immediately upon hitting what appeared to be the end of the runway. It kind of did a bellyflop landing," Jennifer Sorgen told CNN.
"There wasn't a huge explosion of fire, but this was definitely fire, lots of smoke."
An airplane mechanic who witnessed the crash from the airfield also saw the smoke.
"It landed straight, then went to the side and then all you saw was smoke coming off it," Adrian John Mirabueno told the San Francisco Chronicle. "I was scared for the families, and to tell the truth I've never seen anything like it."
Another onlooker said he did see any fire before the plane hit the runway.
"You heard a pop and you immediately saw a large, brief fireball that came from underneath the aircraft," Anthony Castorani, who saw the flight land from a nearby hotel, told CNN. "It began to cartwheel."
Others clarified the plane went into a flat spin around on the ground, as opposed to flipping over.
Helicopter footage showed a trail of debris and blackened pavement starting from the seawall at the very edge of the runway to where the plane finally came to rest in the dirt between the runway and a taxiway.
Amateur pictures and videos of the wreckage were immediately circulating on social media sites, including one from David Eun, a tech executive, who said he survived the crash.
Eun described the immediate aftermath, posting on the Path social media site, "Fire and rescue people all over the place. They're evacuating the injured. Haven't felt this way since 9/11. Trying to help people stay calm. Deep breaths..."
But he soon after posted a more reassuring message, saying "Lots of activity here. Friends, pls don't call right now. I'm fine. Most people are totally calm and trying to let the fire and rescue do their jobs. Just like during 9/11, most people are great and try to be helpful in crisis..."
Another survivor had an even more positive message, telling the Los Angeles Times ""I just want their families to know, most of the people seem OK and we're just letting the paramedics do their job."
The plane, Asiana flight 214, was flying from Seoul to San Francisco with around 290 passengers when it hit at 11:28, Pacific Coast time.