Stanley's health was down to 30% when he finally noticed something that he should've noticed a long time ago.
The woman with the guns could not guard against his attacks at all. The most she could do was dodge and run away. This was most likely the case because the guns by themselves were quite strong, especially with the pushback effect each bullet had.
There were multiple times when Stanley was suddenly stopped before he could get close to her, forcing him to lag behind and take more bullet hits.
Stanley looked at the woman's health. She had lost a fair share of it as well, coming down to 40% herself. Her blue bars were close to full, not that it mattered since she could make use of her special attack even before they were full.
Stanley's own blue bar was going up and was about 70% done. He was certain he could use his special technique before his health fully came down.