Warn him.

"I'm sorry", he says, "but it's very important." He winces at this point and clutches his leg, to show just how very important he means. "You've got to get this painting to Aveugle - I'll do my best to hold them off. Hurry!".

The train stops and its doors open.

You can:

Ask, " Who's Aveugle?".

Say, " Are you deaf? I said STOP BOTHERING ME!".

Wait until the doors start to close then jump on the train taking the painting with you.

Wait until the doors start to close then jump on the train leaving the painting on the platform.