Answer: In general, hallucinations can come in many forms; visual, audible, smell, taste, and feeling... However, in an effort to protect oneself, the person with schizophrenia may personally cause harm to themself. For example, if a person is on the third floor of a building and is in a room with a bunch of snakes (not real) they will do everything in their power to not get bit. That includes throwing objects, cutting things, burning things, or even jumping out of the window.
Another example is a person on the street sees something (not real) coming at them. As a result they jump into the street into oncoming traffic and is hurt by a car, not the thing they were running from.
In addition to that, this is when bystanders could possibly get hurt. Although people with schizophrenia are generally not violent people, hallucinations could lead them to attack another person in self defense of the thing that is not real, but is attacking them.
So, in closing, the object, person (not real)... itself is incapable of causing physical harm, itself. But, a person can get hurt trying to avoid it.
I welcome any questions related to schizophrenia.