Passover (The Black Angels) Easter Egg - Dates in Artwork

On the inside of the album, the left flap has some date written in with the stripes. They are August 1, 1966 - August 9, 1969. The first date is when Charles Whitman killed 15 people in Texas, and the second is the date of five murders by the Manson cult in Los Angeles. There is also written "Exodus 12:12-13", but I don't know what it's a reference to (obviously the bible.)