Puncturing Light

• WWizards of the Coast2010-06-15
  Official Ruling
  A “blocking creature” is one that has been declared as a blocker this combat, or one that was put onto the battlefield blocking this combat. Unless that creature leaves combat, it continues to be a blocking creature through the end of combat step, even if the creature or creatures that it was blocking are no longer on the battlefield or have otherwise left combat by then.
• WWizards of the Coast2010-06-15
  Official Ruling
  The power of the targeted creature is checked both as you target it and as Puncturing Light resolves.
• WWizards of the Coast2010-06-15
  Official Ruling
  An “attacking creature” is one that has been declared as an attacker this combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step.

Rulings via Scryfall