Lexus IS 300 crank, but no start! Security light blinks when key inserted and also when attempting to crank. Also popped hood and alarm went off!

Hello I'm really confused on where to turn next with this car. We
installed a remote wire on passenger side of car for additional
speakers and it worked fine for about an hour. Stopped and filled up
at gas station then headed over to a friends house. Left the car
running (for cell phone to charge) for maybe 5 minutes. I then walk
back out to get into car and shut the door and then the car just shut
off (no sputtering like out of gas) just shut off but dash lights
remained on. I then turned key off and Attempted to restart, no luck.
It would just crank but no start. Opened hood on car then alarm
starts going off, lights, flashers and horn. It finally stopped after
about a minute or so. Got back in the car and inserted key noticing
security light flashing and when attempting to start security indicator
light remains flashing. Need help. Changed fuel pump and I can hear
it when I turn key to the acc position. It's something CRAZY and is
driving me to the point of just putting it up for sale or just giving up
totally! If anyone can PLEASE help all would be greatly appreciated!

Thanks....Kimberly