So this is the second time this has happened and I am getting concerned.  I don’t know what else to call this, but a panic attack.  I have a holland lop/rex mix and he is a little over a year old.  A few months ago a false fire alarm went off and he went completely crazy in his ex pen–running into the walls and whatnot.  This was of course understandable given the noise and luckily I was in the room to catch him.  Just yesterday he had one of these episodes again and I have no clue what brought it on, apparently something frightened him.  We have a school behind our house and sometimes it can get loud from recess all day, but he should be used to the sounds by now.  I just walked into the room, like I do all day everyday and he suddenly sprinted out of his hidey house (which is inside the ex pen) and started slamming himself into the walls of the ex pen, just darting around like he was in some kind of frenzy.  He was going too fast to catch him so I just quickly lifted up the ex pen and then he dashed out and went underneath my bed.  He seemed fine after that.  I get concerned over internal injuries or him getting a heart attack from the fear.  It was so scary to see him banging his head and face into the side of the cage like that.  I am terrified of this happening when I am not home, that he will actually end up killing himself this way.  I don’t know what to do.  I tried searching for a soft mesh fencing to use instead of the metal pen, but I haven’t found anything.  Also I considered buying baby crib bumpers, the fabric tie-on kind.  It will be messy and not look so great, but figured I can maybe line the bottom sides of the ex pen with those and this way if this happens again he will be slamming into fabric vs metal.  I would really appreciate any advice or input you all have on this as far as causes or solutions.  I am so worried.  I find myself surprised that he is such a nervous/easily startled rabbit because I got him as a baby so its very unlikely he has ever been abused and I am always calm with him–never yell or anything.  Maybe it is just in his personality.  He was much calmer as a baby.  Thanks!