Safe Room (for storms) & Panic Room (for intruders) would probably best be separate rooms, as I think about it.
The easiest & safest place to build a solidly constructed Safe Room would be in the basement where you could use the cement foundation wall on at least one side & probably two sides, depending on your layout. It should be designed to withstand the entire house collapsing on it & be able to support your family living in it for a number of days, at least.
Usually, with storms...you can expect to have at least a few minutes warning to get the family together & head down into your safe room.
No such conditions are likely to exist in the event of a burglary/home invasion. I expect that FBI statistics show that most break-ins occur when the family is asleep upstairs, & thus a "Panic Room" would best be located in or near the bedrooms.
(mind you....I have absolutely no facts to back up what I'm thinking/saying here but it makes sense to me!
I think, unless your home is built on a slab, you're probably better off with separate Safe & Panic Rooms, equipped differently for the different threats & probable occupancy time needed.