Multiple log in handle by servlets [требует правки]

I have a small webapp based on servlets and jabsorb. There are two types of users in my app - managers and regular users. Managers can edit users and delete them.

How should I handle the next situation: I logged in as a manager1. Then I open other tab in a browser and log out and log in as a manager2. Then as I go to the tab with manager1 logged in and delete manager2. I should not let it happen so how can I handle that with java servlets?