After Superku's snip use the vec_to_angle() to make the camera look at the player.
modified for manual example
Code:
// get the direction from the entity MY to the entity YOU
vec_set(temp,camera.x);
vec_sub(temp,player.x);
vec_to_angle(camera.pan,vector(temp.x,temp.y,0)); // now MY looks at YOU
EDITED because I mixed up the my and you entities.
