いるところを見つけた

caught someone in the act

→ 居る
phrase Rare #41,957
caught someone in the act Used when someone discovers another person while they are doing something, often something wrong or unexpected. The person doing the action usually comes before いるところを見つけた.
JA: 母は私がこっそりお菓子を食べているところを見つけた。
EN: My mother caught me secretly eating snacks.

先生は学生が試験でカンニングをしているところを見つけた

The teacher caught a student cheating on an exam.

彼らは彼が妹に悪ふざけしているところを見つけた

They caught him playing a prank on his younger sister.