MUMBAI, India  On any ordinary day, Vishnu Datta Ram Zende used the public-address system at Mumbai’s largest railway station to direct busy hordes of travelers to their trains.

But last Wednesday just before 10 p.m., when he heard a loud explosion and saw people running across the platform, he gripped his microphone and calmly directed a panicked crowd toward the safest exit. The station, Victoria Terminus, it turned out, was suddenly under attack, the beginning of a three-day siege by a handful of young, heavily armed gunmen.

“Walk to the back and leave the station through Gate No. 1,” he chanted alternately in Hindi and Marathi, barely stopping to take a breath until the platform was cleared. No sooner, gunmen located his announcement booth and fired, puncturing one of the windows. Mr. Zende was not hurt.

Overnight, Mr. Zende became one of Mumbai’s new heroes, their humanity all the more striking in the face of the inhumanity of the gunmen. As the city faced one of the most horrific terrorist attacks in the nation’s history, many ordinary citizens like Mr. Zende, 37, displayed extraordinary grace.