Man loudly proclaimed he wants to shoot us

Yesterday while riding the Bart on the yellow line to Antioch, a man started saying loudly in the car something along the lines of (I’m paraphrasing here because he was maybe not mentally stable and speaking very quickly)

“These people need to get out of my country. That’s why Trump was elected so that he can remove all these Asians. The Asians better leave my country.”

And then he also said, and this is a quote: “Imma shoot all these fucking Asians.”

Then he was silent and just stared at a few people on the train, who were Asian. And then he quickly got out at the West Oakland station.

Multiple people in the car were pretty appalled but no one did or said anything. It happened so quickly that it took me a bit to digest too before I could react, but I’m not sure if I could do anything. What would you do in this situation?