Respected Sir/ Madam,
I am writing this email to inform you that my name is _____________ (name) and I am a resiting in ____________ (mention room number/ dorm number) on your premises.
I write this email to bring to your notice the suspicious activity I recently noticed. On __/__/____ (date), when I went outside in the lobby/ common area/ any other, I noticed ____________________ (mention what you noticed – uncommon noises/ dislocated furniture/ smoke/ any other) and which became a matter of concern for me.
Therefore, I write this to request you to kindly look into the same and take this into your knowledge so that you can take appropriate action in this regard.
Thank you as always,
[Digital Signature – if applicable]
____________ (Contact details)