When a tumor involves the frontal lobes of the brain, many behavioral symptoms can be seen. Often, people are described by family members as "not themselves". Often, inappropriate actions occur which range from inability to carry on normal functions (e.g. balance checkbook, run household or business) to more severe changes. People can be disinhibited and inappropriate or, on the other hand, subdued and quiet even not moving at all. So certainly your father's behavior could be explained by the tumor. But note, other factors in his illness could cause behavior changes. Medications especially steroids (which are often used to trat the swelling around tumors) can cause behavioral changes. As can metabolic causes such as high blood sugar. Often it is a combination of the above especially as the damage done by the tumor makes the brain more sensitive to behavioral changes from other factors. The fact that a combination of factors could be underlying makes evaluation and treatment difficult. Even, being in a different environment such as a hospital could trigger inapproprite behavioral changes.
Risperidone is a psychiatric medication used to control behavior especially hallucinations without some of the systemic side effects (e.g. cardiovascular) that some other medications can cause. Note that these types of drugs have their own side effects. But certainly, any treatment would be most helpful if some of the correctible factors listed above are, well, corrected. Hope this is of help.
As always, this information is for educational purposes and should not substitute for a physician's evaluation for diagnostic and therapeutic options.
MJD