Technically, a .22 is entirely deadly, and fully capable of killing a human or larger animal. However, unless you know exactly what you're doing or get very, very lucky, it's a recipe for disaster that might leave you facing a wounded animal who's in pain and frantic to defend itself, or an animal in that condition that someone else could come on unwitting. I recommend investing in a .270, or at least a .243, and unless you have already taken one, a firearm safety class if you intend to risk taking a shot. And please, please - always be aware of what's beyond the target you're shooting at.