I recently had a similar experience. I went to a chiropractor and got some immediate relief, rested it for a while, and tried again only to re-injure myself on the first rep of a warm up set at 135. Back to the chiro, stretching exercises (foam roll glutes and piriformis), substituted hyper extensions and Good Mornings for dead lift, squatted very light, and within about two weeks I am back to normal. I switched to sumo and have been able to dead lift the last two weeks, albeit much lighter.
After the injury, I felt pain when loading the spine (taking it off the rack), at the bottom of the squat, and unloading (putting it in the rack). On deads it just hurt right away pulling.