Why do I have a 2 kill streak?

Question

I got two kills and I'm notified with a logo that appears on screen. It's also written "Recon"

I don't understand; I didn't chose the Hardline perk. My kill streak rewards are given when I get 3, 4, and 5 kill streak.

Answer 1

Note that...

• planting or defusing a bomb (depending on the game-mode)
• shooting down or destroying enemys killstreaks
• and some other things

also count for kill-streaks—maybe you defused a bomb wich counted as your third "kill".

Answer 2

I discovered what happened.

I unblocked the specialist kill streak. By default when you got 2 kill streak, you get the perk Recon

Answer 3

It's possible that you got another kill and weren't aware of it, (sometimes mines explode and give you a kill, etc) or that one of your kills was actually a double kill. A 3-kill streak might unlock UAV Recon, which would explain the icon and the notification.

Also, "Recon" is one of the perks, so it's possible that you unlocked some Recon-related challenge, such as Recon Pro.

It's hard to say based on the info you provided, but those are my top two explanations. There's no "Recon" for 2 kills without Hardline as far as I'm aware.