There can always be more done to help those with mental illnesses. Without proper care and awareness from others, events like this are going to keep happening. The more that is done to help people early, the less time the police would have to spend dealing with these cases and celebrities (and members of the public who have dealt with similar situations) could feel a whole lot safer. It has come to be accepted that this is just something that happens to celebrities, but this should not be the case and the problem need to be worked at from the source.
No, there is not a lot more that can be done to stop celebrity stalkers. Stalkers of celebrities become obsessed with the object of their interest and are often quite proficient at stalking their victims. Unless a stalker starts to make threats or exhibit other dangerous behavior, there is not much that the police and security personnel can do to stop them.
People are stalked everyday. Often times they are not celebrities and there is little they can do to stop the person until they've gone too far. Unfortunately this is just part of life, it really has little to do with celebrity other than the advanced exposure. They should have to deal with this problem just like the general public has to deal with this problem from time to time.
No, more cannot be done to stop celebrity stalkers, because there are always going to be a few people who are intent on getting too close. We cannot predict what celebrity is going to be stalked before they are; and we cannot predict which fan will go too far. Unfortunately, we can only react.