A good Samaritan jumped into action when a man with a gun threatening other passengers on a train, held him until police arrived.

Jean-Paul LaPierre, 54, of Boston, said he sensed something was wrong when he boarded a train in Chicago on Oct. 13 on his way to run the city’s marathon as he saw riders rush for the doors.

A rider told him that a man with a handgun was demanding money from people on the train.

LaPierre said he didn’t hesitate to act when he heard about it and also wasn’t thinking about getting shot when he approached the armed man, the Chicago Sun-Times reported.

“I don’t like people that strike fear in people like that,” he said. “I don’t like bullies.”

That’s why LaPierre said he got back on the train and confronted the man entirely on his own. What happened next was caught on video by a passenger still on the train.

LaPierre grappled with the man and held him against the side of the train, pulling the gun from his hand in the process. The man yelled at LaPierre to let him go, but he refused.

“I kept telling him if you move I’m going to knock you out. I’m going to hit you seven times in three seconds,” he said.

“I’m a boxer, I’ll break your head with one punch,” he warned the struggling man and then asked someone to call the police for him.

LaPierre then handed the gun to a man, who said that he could put the safety on and walked it out of the train.

At this point, while LaPierre was alone on the train with the man and his friends threatened him, but he didn’t waiver.

“They started threatening me but I just stood in his face. The guy kept saying to me, ‘It’s just a gun, let me go, let me go.’ I kept telling him, ‘you’re not going anywhere,’” LaPierre said.

According to WGN News,  he held onto the man until police arrived to take him into custody at another stop.

A marathon runner who was threatened moments earlier said she’s thankful LaPierre was there and said he didn’t hesitate to step in.

She said, “Everyone else just sat there frozen.”

Then once LaPierre was off the train, he went on his way and completed his 12th Chicago Marathon.

The police identified the suspect on the train as Tremaine Anderson, 30, and he was charged with one felony count of a man with a firearm.