There are numerous references to Howell and brother Milton in:

Faces of the Confederacy: An Album of Southern Soldiers and Their Stories
By Ronald S. Coddington See pages 236/7 at:

https://books.google.com/books?id=uFpcEsy4UbMC&pg=PA237&lpg=PA237&dq=Confederate+soldier+Milton+V.+Rayburn&source=bl&ots=TGrxcoMVWU&sig=T09lk5rP8XuaPV4BLOer-E4NCB4&hl=en&sa=X&ved=0ahUKEwiZ0arr15TOAhUX-2MKHagwBK0Q6AEILTAD#v=onepage&q=Confederate%20soldier%20Milton%20V.%20Rayburn&f=false

See also:
https://www.geni.com/people/Doc-Rayburn-Bushwhacker/6000000008299228973