Jerrylee Heath almost caught him. He was standing right there.

It was 3:51 p.m. last Sunday. Heath, a train supervisor on duty at Times Square, got a call from Rail Control Center, the operational brain of the New York City subway system, according to an incident report from that day. Someone waiting for a Brooklyn-bound train at Fulton Street in lower Manhattan alerted staff that they had seen someone riding along the back of a departing uptown express train. Maybe Heath could make it to the platform in time, if the person was still clinging to the back of the train.

Two minutes later, Heath was on the platform. As the train edged into the station, he spotted someone just inside the rear cab. The safety cables were detached, and the rear door to the train was open.

It was him, the person who had been with the sole intention, apparently, of being a pain in thousands upon thousands of butts.

“This is a nutcase who is addicted to fucking with the trains.”

Before Heath could take any action, the person pulled the emergency brake—even though by that time the train would have been either barely in motion or at a complete stop—jumped onto the track, and dashed from the direction the train came, back towards 34th Street.

Without police present and Rail Control Center’s approval, Heath was not allowed to follow him, per New York City Transit work rules.

For the next 18 minutes, Heath rode downtown, then uptown again, to see if he could spot the culprit. But at 4:11 p.m., he radioed to Rail Control Center to deliver the bad news. “The unruly person,” as he was called throughout the incident report, got away. Again.

Heath could not be reached for comment prior to publication. But the incident report from that day, along with 19 others obtained from various sources inside the Metropolitan Transportation Authority by Jalopnik, paints a detailed picture of how a suspect believed to be one sole subway supervillain has disrupted tens of thousands of customers’ commutes over the course of several months.

According to statistics in the incident reports, since March of this year, 747 trains have been either delayed or cancelled as a result of service disruptions caused by the same pattern of behavior.

This is not to say the suspect has personally tampered with nearly 750 trains in three months; each time he pulled the brakes, it delayed some number of other trains behind it. And those are just the ones officials know about. The actual number could be much higher.

The pattern outlined in the reports is unique: the emergency brakes are activated under mysterious circumstances, only for the conductor to find the back cab door unlocked, rear door to the train open, and safety cables unattached.

Each incident report details one “spree.” Many involve only a single train’s brakes being activated, which would delay trains behind it, depending on how busy the system is at any given time of day. But some involve the suspect triggering multiple trains’ emergency brakes, which can have a multiplier effect of sorts, as backups become more severe in both directions causing cascading effects on both the express and local lines. In some instances, he was able to delay more than 100 trains in a single spree.

To be sure, 747 is a tiny fraction of the overall number of trains delayed during that time period. In total, 74,220 weekday trains did not reach their terminal station within five minutes of the scheduled time during the months of March and April, mostly the result of myriad of problems for which New York City Transit cannot blame rogue actors.

But most of those 747 trains were rush hour trains, some so crowded with passengers the conductor couldn’t get to the rear of the train in a timely fashion. And all those customers, sometimes more than 1,500 per train, were delayed for reasons still unknown.

Monday, March 11 at 6:27 p.m. is the first known time he struck with his signature moves, according to the reports that fit the description of the perpetrator’s M.O. But it could have been sooner.

The conductor of an uptown 5 train at Grand Central saw him climb down onto the track bed from the rear car as she went to inspect why the emergency brakes had mysteriously been activated. The rear cab was unlocked, safety chains unattached, back door open.

He was spotted six minutes later riding on the back of a downtown 4 express train departing Grand Central. A few minutes later, that train’s brakes were activated, too, while adjacent to the local 28th Street station.

His strategy, such as it is, seems to be to ride on the back of an uptown train, most commonly the 2 or the 5, to a major express stop. He will then pull the emergency brakes, maneuver via the track and across the platform to a train headed in the opposite direction, and do it all over again, plugging both directions of service within minutes.

Sometimes, he will wait until service resumes uptown—typically 10 to 20 minutes after the brakes are activated—and then disable another uptown train again, causing a cascade of cancellations and delays that can take more than an hour for the subways to recover from.

Tuesday’s spree, which saw emergency brakes activated on three different trains within a 36-minute span, delayed or cancelled 118 trains during the peak afternoon rush on the 1, 2, and 3 lines. Dashing between trains during that encounter, he attempted to climb aboard a 2 train from the rail bed only to see the train’s conductor. He smiled, made an “obscene gesture,” according to a telephone interview between Rail Control Center and the conductor hours later which was noted in the report, and sprang away. It was his most disruptive day yet.

At Wednesday’s Metropolitan Transportation Authority board meeting, New York City Transit president Andy Byford said the suspect almost certainly gets into the cab to activate the brakes by using a key available to any train operator or conductor. However, he did not venture a guess how this person obtained a key.

Transit officials referred the case to the NYPD Tuesday night. It’s not immediately clear what potential criminal charges the person could face if caught that would sufficiently capture the degree of ire he has garnered from straphangers. People who go onto the tracks without authorization are , just a misdemeanor.

For his part, Byford seems aware of this.

“What I’d like to do, with the legislature, is to get very harsh penalties in place for people who commit anti-social behavior, in whatever form that takes, I would love to be able to catch these people,” Byford said after Wednesday’s board meeting. “I would like them to face the consequences of their actions, and I’d like to ban them from the subway. Right now we don’t have that power. We are actively seeking it.”