An alarming but ultimately harmless incident aboard Metro’s Red Line on Sunday points up the difficulty of policing an urban subway system with 118 miles of track — but also the persistent concern by some riders that the agency should do better at keeping order on its trains.

A Metro rider who was returning home with his family after a weekend outing at a Washington museum said he had to use the train’s emergency intercom to summon help after a deranged man burst into the car and began cursing and ranting about the Islamic State.

But nobody came, and the Red Line train kept going, the rider said.

Two more stops went by as the agitated man continued to act in a threatening way, according to the rider — a Montgomery County resident who asked to be identified only by his first name, Andrew, because of safety concerns. At one point, he and his family switched cars but the frenzied man followed them and demanded to know whether they had summoned the authorities.

After the third stop, Andrew and his family exited. He called for help again from an emergency call box on the platform and watched the train depart, still with no sign of police. What bothers him the most about the episode even now, he said, was that instead of holding at a station for police, the train kept rolling.

“That train shouldn’t go anywhere until a security person or police get down there and find out what’s happening,” Andrew said Tuesday in an interview. “It was shocking to me how poorly they handled it.”

Metro offers a strikingly different account. In response to questions about the incident, Metro spokeswoman Sherri Ly said police met the train three minutes after being summoned and removed the disorderly person. No one was hurt. Ly also said Andrew and his family did all the right things in a dicey situation.

“If you feel uneasy about something happening in your car, exiting at the next station and moving to another car is a good thing to do,” Ly said in an email. “Using the intercom to notify the train operator was also the right thing to do.”

Andrew isn’t buying it.

“They just got lucky nothing bad happened in what must have been a 10- to 15-minute period of time,” he said.

Andrew, a financial adviser who rides Metro a couple of times a month, said he headed to the Metro, along with his young daughter and extended family from out of town, after  a visit to the Smithsonian National Museum of Natural History. They boarded at Smithsonian station and then transferred to the Red Line at Metro Center aboard a new Series 7000 train.

Somewhere around Farragut North, a man burst through one of the doors between train cars, cursing and babbling about the Islamic State terrorist organization. He also bent over as if to peer into the faces of passengers who weren’t there and screamed at them. Then he lay down on the floor, staring in the direction of other passengers and asking what they were going to do about it.

At the next stop, Andrew and his family switched cars. He also used the train’s emergency intercom to report the situation and provide a description of the disorderly passenger.

“Okay — we’ll take care of it,” he was told.

The train’s doors at Dupont Circle remained open for what seemed like an extended period, Andrew said, so he thought Metro Transit Police officers would appear at any moment.

Instead, the train departed, and moments later the crazed man burst into their car again, this time overpowering another passenger’s attempt to hold the connecting door shut. The agitated man also wanted to know who had used the emergency intercom.

When the train pulled into the Woodley Park-Zoo station, Andrew and his family exited. This time, he used an emergency call box on the platform and reached the station manager.

“I said, ‘Did you guys get my emergency call from the train? Nothing’s happened,’ ” Andrew said.

“Sir, we’re on top of it,” he was told.

“You’re not on top of it, because you got to get this guy off the train,” Andrew recalled saying. “You shouldn’t have pulled out of the previous two stations with this guy on here.”

The station manager asked Andrew whether he had called 911.

“No, I called you guys,” Andrew recalled saying. “Isn’t that what the emergency button is for?”

Metro police received the report of a disorderly man aboard car No. 7263 at 3:31 p.m., via the Rail Operations Control Center, Ly said.

“The train was at Woodley Park traveling in the direction of Shady Grove,” she said. “Officers intercepted the train at the next station, Cleveland Park, at 3:34 p.m. and removed the individual from the train.”

Andrew, after hearing Metro’s account, expressed doubt about the response. He said he believes the agency only took action after his second attempt to summon help from the platform, not the first attempt when he was on the moving train.

To him, the episode suggests that Metro employees say they put safety ahead of other concerns, such as on-time performance, but still don’t act like it or they would have held the train.

“They haven’t gotten the message,” he said. “I think most people would rather be late than injured.”

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