What is the ruling of Islamic law concerning a young man who beat a man, stole his phone, and blasphemed against Allah Almighty?

What was mentioned in the incident, namely the aggression against the oppressed and cursing Allah, is reprehensible. Cursing is an act of disbelief that expels one from the fold of Islam. It is obligatory upon anyone who witnessed the incident to denounce the oppressor, restrain him from his injustice, and assist the oppressed, based on the Prophet's (peace be upon him) saying: "Help your brother, whether he is an oppressor or oppressed," and his saying: "A Muslim is the brother of a Muslim; he neither wrongs him nor abandons him." Supporting the oppressed is obligatory when one is able and safe from harm. It is a communal obligation (fard kifayah) and falls under enjoining good and forbidding evil.