Screenshotting a snapchat

[wildpitches]

My Friends are able to take a screenshot of a snapchat picture from their phones. I have a HTC Evo Design 4G and I know how to normally take a screenshot from my phone (hold down the power button and press the home button), but when I try to do this while looking at a snapchat picture it doesn't work for me. Anyone know how to do it from my model of phone?

 

[wildpitches]

And don't get me wrong, I'm not doing this to be a dirty guy, my friends don't send me naked pictures (most of them I wouldn't want to see more than 1 second anyway...)