Another possibility is that you got that guy that reacted first (I'll call him first guy) then the bullet ricocheted off the wall and hit the other guy (I'll call him second guy) and then the first guy you hit lagged and the second guy didn't. The second guy got killed first because of the other guy lagging then a split second later the first guy got killed. Yeah I believe the Aim Assist in Destiny is 'too damn high' but if you think of a game with next to no Aim Assist on snipers (COD for example), a sniper can kill with one body shot. If you ask me that kinda evens it out.