To shoot oneself in the foot means to make a situation worse for oneself without meaning to, without intending to.
搬起石头砸自己的脚,意思是无意地让情况变得更糟。
一个叫欧维的男人决定去死
He's assuming that there's a good deal of splattering when one shoots oneself in the head, and he's loath to leave more of a mess behind than he has to.