Go to the part where the musketeers start saluting

D'artagnan, Athos, Aramis, Porthos, and Philippe for their magnificent valor. When the king starts making his way through the musketeers, look at his right hand. You can see him pull out a knife. Then just as he starts to try to stab Philippe, you can hear the king unsheathing another knife, which was in a holster at the front of the king's armor when he pulls out the other knife.