There is a friend who has been diagnosed with been schizo illness is it normal for him to threat his family members and telling them his gonna kill them.and he says ih with so much madness.his been hospitalized a couple times cause he over acts and becomes agressive. He has attacked one brother behind his back and started chokin him saying his going to kill him. The parents come out and get him ooff the brother once he lets go he walks down the stairs with pride because he was choking his brother. What can we do to keep him away