Deadlock scenario

Had a deadlock this morning with two users running this statement.

UPDATE DC_SHIP_WAVE SET WCS_DOWNLOAD_DATE = GET_DB_DATE_TIMETrying to wrap my mind around on how the deadlock could occur.  During different periods of the day this can be an active table (approx. 300 rows at any one time).   Wouldn't each user have to run this statement twice (without committing the first time) for this deadlock to happen?  Or could it have been a timing thing where each user was issuing the update (only once) while active changes were being made?I plan on digging into this further but just wanted to get some possibilities in mind before sorting this thing out.