All of a sudden, the sea lion emerged out of the water and grabbed hold of the girl's dress and pulls her into the water.
Otjen said it is possible the sea lion thought the little girl might have more treats.
Danielle Hyson, a trainer at the Vancouver Aquarium, told CBC that the girl's family should call the aquarium if she had suffered any injuries.
He says the harbor is on the sea lions' migratory route and that males sometimes swim into the area looking for free food.
SFU student Michael Fujiwara was on the dock when he saw the large, male sea lion approach, so he started filming it as a crowd gathered around the animal.
NAIJ.com gathered that a man jumped into the water to rescue the girl. They say doctors might not know about the specific course of treatment that would be required, and want the family to reach out so they can ensure she gets the help she needs.
"They were pretty shaken up", Mr Fujiwara told CBC News. He also said he's happy to hear that no one was injured in the incident.More news: U.S. evangelical green groups pan Trump's climate accord exit
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"You can not think these are characters out of a Disney movie", said Andrew Trites, UBC Marine Mammal Researcher.
"When we see performing animals, like at the circus, we get false information about whether animals like to be around people".
It begins with the sound of cameras clicking and onlookers marvelling at the size of a California sea lion that people are feeding.
Baziuk says that they've been warning visitors not to feed the animals for years.
"Now we finally have something out there that's going to grab people's attention and show them exactly why they shouldn't be behaving like this".
"You wouldn't go up to a grizzly bear in the bush and hand him a ham sandwich, so you shouldn't be handing a thousand-pound wild animal in the water slices of bread", said the official.
Trites hopes the video of the encounter teaches others to not feed wild animals like sea lions.