A 21-year-old man was arrested for allegedly killing his mother's paramour late on Monday at a bus stop in Bandra-Kurla Complex here, the police said on Tuesday.
The accused allegedly suspected his mother of having an affair with the victim Parvez Sheikh, an official said.
The incident occurred at around 10 pm on Monday, when the accused came to know that his mother was sitting at a bus stop with Parvez, he said.
He then rushed to the spot and attacked the victim with a paver block, smashing his face, he added.
While passersby caught hold of the accused and handed him over to the police, Parvez was rushed to a nearby hospital where he was declared dead, the official said.
"The accused is a student of M H Saboo Siddik College, where he is pursuing a diploma in electronics," senior inspector Pradip Bhosle of BKC police station said.
The accused has been arrested under section 302 (murder) of the Indian Penal Code, he added.