The first time we see the raid on the senator's room, 2 security guards are shot in the head. The blood spray from the second one emerges a fraction of a second before the gun fires. The second time the raid is played out, everything happens exactly the same way, but this time the spray matches the gunshot.
Ben Barnes plays Frank Castle's friend Billy Russo. In Stardust he played the father of Charlie Cox, who plays Daredevil in another Marvel/Netflix series.