https://pre00.deviantart.net/34eb/th/pr ... ceedgz.png
( author's comment)
Too slow.
Step1.
Eliminate the sentry.
Step 2.
Steal her uniform.
Step 3.
Take her place.
Step 4.
Wait change of the guard.
Step 5.
Total access to the facility.
The 3 first steps are the more important. It have to be done as quickly as possible, for obvious reasons.