Police have arrested a motor mechanic who stabbed a 16-year-old boy in the stomach for stepping on his foot while alighting from a BEST bus on Tuesday afternoon. Police said that after the victim got off at the bus stop in Teli Galli, Andheri (E), an argument ensued between the two and in a fit of rage, the accused pulled out a knife from his pocket and stabbed the teen in the stomach and chest several times.