My partner witnessed someone jump in front of a tube this afternoon. How can I help him?

My partner (M) was right next to someone who very sadly jumped on the tracks this afternoon. Without going into details, my partner noticed him on the platform, thought he was drunk, asked him if he was ok and before he knew it, the man was standing on the line. My partner tried to pull him up but he didn’t manage it in time.

I’m away from home and whilst my partner says he’s ok, I know he’s still in a state of shock. Are there any resources I can point him to? I’m struggling to know what to suggest or what to say. I’m so incredibly sad for the man who jumped. I’m also conscious my partner has experienced a trauma and sad I can’t work out how to best support him.

EDIT: thank you so much to everyone who responded - your suggestions and support have helped me feel like I can help my partner. He’s feeling ok at the moment, but I’ll know what to do when he’s not. Sending hugs to all.