Criminal justice class discussion post

Officer P, a university police officer, received information that a student living in a campus dormitory was selling drugs.  This information was conveyed to Officer P by an anonymous caller to the officer's cell phone.  Officer P knew the suspect in question and had similar suspicions.  Officer P immediately went to the dormitory and stopped the student as he was leaving the building.  Officer P arrested him, searched his pockets, and found drugs.

Were these actions valid?  Justify your answer.