The drama peaked midmorning when the bear was discovered - and shot dead.
The 74-acre zoo offers many attractions including a cable vehicle and a miniature village.
In addition, wild animals have broken out of the zoo.
It was not immediately clear how or when exactly the animals escaped, but heavy thunderstorms overnight had resulted in bad flooding across the zoo, which is on a riverbank. The gorilla was tranquilized by veterinarians and returned to his den.
The storm had caused widespread devastation in the region, where many residents were Friday clearing muddy water from their cellars and removing downed trees. The five big cats were found within the confines of the park and were recaptured in the afternoon.
In an earlier zoo incident two year ago, two lions broke out of their cages at the Leipzig zoo.
One of the lions was shot dead and the other was eventually brought back into captivity.
In 2015, an orang-utan was shot dead after escaping from the Duisburg zoo, and a bear escapee from Osnabrueck suffered the same fate in 2017.