After being entirely absent from the marketing for Infinity War and the film itself, bow-and-arrow aficionados finally get their long-awaited first look at Hawkeye as Ronin in this trailer.
In a very comic-accurate outfit, Jeremy Renner shows up in a handful of brief shots using a katana to kill several thugs on a street in Japan. This is a marked difference from the last thing audiences knew about Clint Barton, as in Infinity War, it was stated that he took a similar deal to Scott Lang after the events of Civil War in an attempt to keep his family safe.
So what brings him all the way to Japan to become a ninja? Well, historically speaking, his family's death. That's what turned him into Ronin in the comics and there's a strongchance the same will be true here. But, the crucial thing to note is that there is an even stronger chance that they were actually dead before the snap.
When Black Widow comes face-to-face with him in the trailer, Natasha looks exactly the same as she did in Infinity War. Similarly, there are tons of other hints in this trailer that very little time has passed since the end of Infinity War. So in order for Clint to have already had the time to move to Japan and train to become Ronin, his family must have died before the events of the snap.