Tenno Of All Trades achievement

[Sadimitsu]

I was running a Meso fissure survival mission at 4:50am on Draco when i got this achievement. I was playing as Chroma prime with Daikyu, Sancti Magistar and Carrier prime in my load out with no secondary weapon equipped.

The achievement is to score a kill with your primary, secondary and melee weapon within 5 seconds or less, problem is i got the achievement with no secondary weapon equipped.