Updated

A seven-ton bull elephant charged and killed a female elephant half his weight Wednesday as visitors to an Israeli nature park looked on in horror.

Officials at the Safari park near Tel Aviv said they were unable to stop Yossi, a 33-year-old male, from attacking Atari, the 46-year-old matriarch of the captive herd, and trampling her to death.

"What happened to Yossi, who grew up all his life with Atari, and they always got along?" Yigal Horowitz, a veterinarian at the park, told Israel Radio. "Here and there were small fights, but they never had a fight like this one."

Elephants observe hierarchies and visit places where others of their herd are buried. But scientists have recently become increasingly concerned with what they say is a rising level of violent activity among the large mammals.

In a 2005 essay in the Journal of Nature, Oregon State University psychologist Gay Bradshaw argued that the worldwide population of elephants is suffering from a form of post-traumatic stress disorder, making them excitable and prone to violence.

Horowitz said the nature park's staff will make a decision about what to do with Yossi after investigating the incident and consulting with outside experts. In the meantime, Bati, another female with a senior role in the herd's hierarchy, is expected to take charge of the herd.