Lion kills lioness at Dallas Zoo

A lion at an American zoo suddenly turned on a lioness in their enclosure and killed her in front of horrified families.

Officials at the Dallas Zoo in Texas said they had no idea what caused the attack.

The pride of five - two brothers and three sisters - had lived together "peacefully" for years without incident, the zoo said.

Then on Sunday, one of the males wrapped his jaws around the neck of a five-year-old lioness named Johari. She died quickly.

"Johari was a remarkable animal, as are all of our lions," said Lynn Kramer, vice president of animal operations and welfare at the Dallas Zoo.

"This is a very rare and unfortunate occurrence. In my 35 years as a veterinarian in zoos, I've never seen this happen."