What are your thoughts on altruism, and can true altruism exist, or do all acts of kindness ultimately have some self-serving motive?

Man standing on a train platform. Notices a child fall onto the track ahead of an approaching train. Child is crying but not otherwise moving. Man has one second to act, and leaps to the tracks, pushes the child out of the way and to safety, knowing that he himself will be killed. And he is killed.

Altruistic, or not?