Paula Simons: A very public crime; a very private investigation

It happened last Wednesday at about 10:30 p.m. 
Two 28-year-old brothers —  twins — were standing in a bus shelter on 118 Avenue at 83 Street, near the Catholic Social Services building. According to police, the 28-year-old men had just gotten off one bus and were waiting for a transfer.
They were approached by a mugger, who tried to rob them. But the robbery went wrong, and one brother was stabbed. The robber took off, and the twins chased him east along the avenue. B