KANSAS CITY, Mo. -- You've heard of running with the bulls in Pamplona, but on Monday afternoon, two boys decided to run with the hippos at the Kansas City Zoo.

Gill Marie, 14, and her aunt were touring the zoo when they noticed the boys were throwing rocks at the large mammals.

"There were two boys that jumped into the hippo area and were trying to antagonize the hippos," a witness said.

The hippos soon started charging at the boys.

Marie called security and yelled at the boys to stop and get out of the way.

"I was trying to tell them to get out or they would get killed. They could've tripped and the hippos could've stepped on them," Marie said.

She said she knows a lot about the dangers hippos pose when provoked.

"I was watching Animal Planet, and they kill more people than crocodiles, snakes, anything else when they're in the water. They can crack boats in half," Marie said. "I was telling them, 'Don't go in there unless you want to get killed because they're, like, around two tons they have really big fangs.'"

The animals charged the boys several times before they climbed out of the pen.

Security took the boys into custody. Police said they will probably face tickets for trespassing and harassing the animals.

Marie said she can't imagine what the boys were thinking.

"They were really stupid, unless they were trying to do suicide by animal," she said.

The zoo director said the boys, both 14, are from St. Louis and were apparently trying to impress a girl. The director said the zoo will press charges.