No assassin worth using to kill a head of state uses a laser aiming system. Lasers go both ways. To breach the clear shield around the podium would probably take a 20mm, since .50s with a raufoss are common enough in defense circles.
I had originally missed the glass shield; saw it but didn't register it at first.
The Gateway Pundit offers: One viewer says this was a reflection in the bullet proof glass on the president. It may have been emitted from cameras using red-eye reduction(?).
Perhaps... not overly convincing. It is notable that a glass shield was erected in the first place; maybe that is standard these days. Happy Christmas Mr. President.