This post has been updated.

A man was assaulted aboard a Red Line train between Union Station and NoMa-Gallaudet University during Monday’s evening rush, according to Metro.

Metro officials said they received a report about 5:30 p.m. of an assault on a Red Line train that was approaching the NoMa station. In a statement, Metro spokeswoman Morgan Dye said a transit police officer who was on the platform “intercepted the train and stopped three juveniles” who ran off the train when it stopped. The youths could not be positively identified as suspects in the attack, Metro said.

Lori Kaplan, the wife of the victim, said Tuesday that her husband, whom she did not want to identify, was “terribly concussed” and suffered a broken jaw. He was undergoing X-rays and MRI exams.

Kaplan, senior director of audience insights at NPR, said she meets her husband every day at the NoMa station platform. About 5 p.m. Monday, she said, he texted her to say that there was an “idiot gang” in the first car and that he was going to move cars. Then, she said, he went silent.

Kristin Smyth, 28, an economist with the federal government, said she boarded the Red Line train at Union Station shortly after 5 p.m. She noticed a large, rowdy group of youths. “It started with two of the kids, two boys, egging each other on,” she said. ” ‘You bet I won’t do it. You bet I won’t do it.’ ”

She said one of the youths approached a man who appeared to be in his 30s and asked for his bag. The man remained calmly in his seat, she said, when one of the youths began throwing punches. In an email, Dye said the attack stemmed from an apparent attempted robbery of the bag.

Smyth said the punching continued maybe “30 seconds or so” when the victim, who appeared dazed, started to walk away from the youth. That’s when “the second kid jumped in and punched him square in the jaw,” she said.

She said the man passed out and hit the floor of the train’s front car. Smyth bolted toward the operator and knocked on the window.

“You’ve got to stop the train! You’ve got to get the police and the medics!” Smyth yelled.

Later, she said, the victim stood up and made his way to the front of the car.

“And his face was bloody, and he just kept saying, ‘What station is this?’ ‘Is my wife here?’ ” Smyth said.

He also asked, “Did I do something wrong? What happened?”

Smyth said the doors to her train car didn’t open when the train pulled into NoMa Gallaudet University station. It seemed the driver wanted to keep the youths trapped, she said. Metro Transit Police officers were on the platform, and when the operator spotted them, he pointed out the group believed to be responsible for the attack. But some of the attackers escaped, Smyth said, likely passing through the emergency doors and then boarding another Metro train in the opposite direction.

Eventually, she said, the victim met his wife on the train platform and laid his head down. An ambulance arrived shortly thereafter, the man’s bloodied face becoming worse by the second, she said. Kaplan said she mouthed “Thank you” to a few witnesses who stepped in as she walked her husband to the ambulance.

“His face — I’ve never seen a face looking like that. His face was ballooned out, his mouth was all bloody,” Smyth said. He told her that he could could feel himself losing teeth, Smyth said.

Smyth said witnessing the beating left her shaken. She rides the Metro from Brookland to her job in the Union Station area. Metro Transit Police spoke to her and several other witnesses she said.

“I just keep seeing that guy’s blood everywhere, and it was just at rush hour!” she said.

Dye said the investigation is continuing and will include a review of video surveillance for suspects.