So, here is my commandblock code:

/tellraw @a[team=Federation] {text:"[StrikeZone]", color:black, extra:[{ text:" @a[score_streak_min=5,score_steak=5] is on a killing spree!", color:red}]}

But it shows up as

[StrikeZone] @a[score_streak_min=5,score_streak=5] is on a killing spree!

I want it to show the player's name rather than the @a[stuff]. Help? Thanks!