Quote: "...a gentle and kind person, who assists us in nursing stray and abandoned puppies and kittens, we had no idea why this was happening."
You do realize that this is exactly the sort of thing that some the people who were being used by some of the most terrible criminals would say about them? Even if he had done terrible things in his past, heck, was still doing them at the present time, it would have been to your friend's advantage to present himself to you, the people who were providing his cover as a gentle and loving soul, kind to puppies and kittens.
Also, any person who is on parole is strictly restricted from living with, associating with, etc. people who have in their pasts had common interests, such as other known felons, and they are very particular about whether or not he lives an a place with guns. I almost get the perception you lied to the police about that issue.
Quote: "To keep things simple, I said, "No (I keep my family at the mercy of intruders and bad people)."
You must accept that you may unwittingly have put your family at the mercy of bad people who lied to you and misrepresented themselves anyway. You couldn't just use your powers of discernment to automatically be able to identify whether or not this person is evil at heart or is likely to re-offend. And it is a VERY bad idea to lie to the police. People who are sometimes in dangerous situations involving them do not take kindly to being lied to about and then finding out they've been lied to about weapons.