[An off-duty cop allegedly attacked a train conductor; UPDATES BELOW] Commuters aboard Manhattan-bound J and M trains were stuck on the Williamsburg Bridge for nearly an hour during this morning's rush hour, due to NYPD and FDNY activity at the Essex Street station. Others were forced to give up on the J and M entirely after Manhattan-bound trains stopped running. It's unclear exactly what happened—the NYPD hasn't released any information about the incident—but video taken from a train inside the station shows someone trying to calm down passengers:

One passenger trapped onboard a J train stuck on the bridge tells us an MTA worker spoke to the straphangers in her car some 40 minutes after the train stopped and told them to "please call the MTA and tell them to stop running these old trains." The MTA worker also declared, "Someone was hit by the train." The MTA told a reporter with NY1 that a conductor was assaulted:

An FDNY spokesperson tells us one person was transported to Beth Israel Medical Center, but could not elaborate further. For now, there are no J or M trains running into Manhattan, and trains are terminating at Marcy and Myrtle Avenues, when possible. Delays are ongoing.

We will update when more information becomes available.

Update 10:30 a.m.: CBS 2 is reporting a conductor was assaulted on the train, and pulled the emergency brake, according to the MTA. The person who allegedly assaulted the conductor is now reportedly in custody.

Update 12:58 p.m.: The Daily News reports that an off-duty cop has been arrested for allegedly assaulting a conductor onboard a J train this morning, causing the subsequent delays. The tabloid reports that the cop, who has not been identified, had been standing near the door to the conductor's booth, and was struck when she opened it—he then allegedly became enraged and shoved the conductor, who fell and suffered a mild injury. She then pulled the emergency brake.

When contacted, the NYPD was unable to confirm an arrest.

Update 2:20 p.m.: The Transit Workers Union Local 100 President John Samuelsen issued a statement, "Once again we see that the transit workers have jobs unlike any other. They deserve every penny they earn - and then some. Transit workers risk being attacked and abused like this everyday as they move millions of bus and subway riders. Just a few weeks ago, a lunatic set fire to a token booth with an agent inside. It's a very stressful environment. It's certainly isn't an easy way to make a living."

The off-duty cop has been identified as Tremel Davis, 33.

Update 3:35 p.m. The NYPD has confirmed off-duty cop Tremel Davis, 33, was arrested today and charged with assault in connection with this morning's incident.