A man coming home from an overseas trip. Another on his way to work. A woman off to a celebratory dinner.

They were three New Yorkers riding the subway on a Sunday afternoon in September, not knowing they would soon end up in a hail of police bullets meant for Derell Mickles.

Mr. Mickles, 38, had slipped into the Sutter Avenue L station in Brooklyn without paying. Two police officers had followed him to the elevated platform, catching a glimpse of a knife in his hand. Within minutes, the police would shoot two of the passengers, Mr. Mickles and one of the officers.

The harrowing episode was a stark example of how even seemingly normal commutes can erupt in a flash of violence in a transit system officials have struggled to safeguard for the millions of New Yorkers who rely on it every day.

Subway crime dipped overall last year, but felony assaults were up 55 percent since 2019. There have also been alarming random acts of violence, like the immolation of a woman at a Brooklyn station and the shoving of a man into the path of a train in Manhattan.

Gov. Kathy Hochul and Mayor Eric Adams have responded by flooding stations with law enforcement: 3,250 police officers; 1,250 National Guard soldiers and state troopers; and another 300 officers on overnight trains for the next few months.