I would, but then again I have nothing to hide to start with. Apparently neither did the other witness who voluntarily came forward and called police.
IMO JLM had several days to contact a lawyer. A competent lawyer would have offered to represent him immediately especially given the high profile and emotional nature of this case involving UVA and Charlottesville. Lots of free publicity and plenty of prestige amongst his law buddies.
A competent lawyer would have also advised him that it was in his best interest to voluntarily submit to police questioning, with his lawyers present, instead of making the police come looking for him with a search warrant as well.
I can only think of one reason why he didnt contact police and didnt contact a lawyer and thats because he was hoping he wouldnt be caught.
He may have something to hide, hence the actions by LE.