Seizures After Brain Tumor Removal

A very good friend of mine was diagnosed with a brain tumor a few years ago. He was initially classified as Inoperable. Six month MRIs showed little or no grow, however, he began getting horrible headaches and found a surgeon in San Francisco (he's in Chicago). He had the surgery and the surgeons reported that 70% of the tumor had been removed which was much more than they expected to accomplish. The first week after the surgery he was doing very well, completely coherent. Same person, same personality. A couple of weeks past and he started getting symptoms such as forgetting words in the middle of sentences and occasional babbling.
Six weeks later things have changed dramatically. At first the doctors suggested that the brain slowly became accustomed to this mass (tumor) over many years before he had symptoms and was adjusting to this new 'space' in his brain. He was getting progressively better. Occasional babble would come out of his mouth but him and his wife just dealt with it and actually found some of it quite amusing as long as it was a 'normal' thing.
Last week my friend started having seizures and complete loss of coherent conversation and mild seizures (mostly twitching). He is back in the hospital in Chicago and, to me, it sounds like the doctors have no idea what's going on. They have drained excess fluid from his brain as he had developed swelling on the outside of the head on the same side of the head where the tumor was/is.
As a layman it kind of makes sense to me that the brain had slowly become accustomed to this foreign object slowly growing in his brain and grew around it. Now, suddenly there is this void in the brain that it has to accommodate. So, in my mind this makes sense.
I wish I knew more specifics about the type of tumor and the location but I just don't know at this point.
Has anyone had a similar experience or a loved one that has gone through this? Does my logic make sense? He was supposed to be getting radiation to attack the 30% of the tumor that they couldn't get to but since this setback that has all changed.
Can someone help me to understand this and hopefully give advice and comfort to his wife and friends?