Issues with older cat growling and attacking me

Question
I have an older (12+ year old) black-and-white male tabby that has been an indoor cat all his life.  I live in a quiet home with my brother, who owns an older (8-10 year old) female calico cat.  My brother and I went to visit family for a few days and left our cats home alone (which we have done before without problems, they are usually very well behaved).  However when we got back my cat started acting moody and hid under my bed.  When I went to check on him he started screaming "mad cat" noises and viciously attacked my hand with his claws and teeth, giving me several very nasty gashes and severe bleeding.  For the rest of the day he growled and hissed at me if I was anywhere near him, and I have no doubt he would have violently attacked me again if I got too close.

I ended up chasing him out of my bedroom while holding pillows and a blanket (I didn't want to be attacked in my sleep).  He seems to be a lot calmer today; I left him completely alone to calm down from whatever upset him, and he finally came out of hiding, ate some food, and let me pet him.

I figure he was just upset about me being gone for 3 days and "all is forgiven." But when I called him in to my bedroom for bed (as usual), he started coming in but stopped outside the door and refused to enter.  Then he started growling and hissing again.

I'm completely at a loss!  Is this normal?  I have no idea what triggered the attack or why he's so upset; the other cat is just fine, so I don't think anything odd happened while we were gone.  Do you have any idea what might have caused a usually mellow and calm older cat to attack so viciously?

Answer
Lee,

The usual cause of this type of behavior is that some neighborhood cat was lurking around your house and he saw it out of a window and went into that flight/fight/fright mode.  When cats are in this mode they forget all about relationships and are just ready to do whatever they need to to "survive".

Usually, this all calms down in a couple of days.  One way to deal with it is to put the cat into an interior room (no windows) for a few days as a "time out" to let him calm down.

Best regards... Norm.