Can the big "X" sign be used for purposes other than runway closure? About last Sunday night in the dark I was departing LAX on a redeye.  We pulled away from the terminals (maybe 500m?), made a right. Looking back out the window I saw a BIG lighted X (maybe 20? 30? foot high - really bright!) flashing. I guess it was one of THESE but it had four rather than five per arm and REALLY bright.  (I grabbed a completely hopeless video; I'll try to add it later.)

Now, just the previous day there was that incident at LAX where an airliner hit a supply truck, and toppled over the truck (some people in the truck were hurt even I believe).

Can the sign be used on situations other than runway closure? For example:


almost certainly some drama, such as the mentioned truck-jumbo incident, or 
is it actually just a normal control sign that goes on an off?  (Perhaps, to indicate "don't cross here, someone else is crossing" - or whatever.)


My impression was that it was at the "side" of a runway  or taxiway, that is to say, as if crossing it.  (Of course, my impression could be totally wrong.)  Would these Xs be used in that way, or, only at one end of a runway?
There are a couple of different NOTAM's stating runway closures at KLAX, including the below. Bear in mind that runways are closed regularly for maintainence (resurfacing) just like roads. No drama about that.

LAX 05/189 LAX RWY 07R/25L CLSD DLY 0800-1300 1705300800-1706011300
LAX 05/157 LAX RWY 07L/25R W 1300FT CLSD. DECLARED DIST: RWY 07L TORA 9665FT TODA 9665FT ASDA 9255FT LDA 0FT. RWY 25R TORA 10808FT TODA...
LAX 05/156 LAX RWY 07L CLSD TO LDG 1705252200-1708190659

There are also several closed taxiways.