What to do with injured baby squirrel?

[Edit: Situation handled, see comments below] So there is this injured baby squirrel along my walk home from work. Slow moving and slightly bleeding, occasionally tries to walk or climb but doesn't go far; feisty enough to jump and hiss (but not run away) when I approached with a not quite big enough box. Wildlife rehab center closed for the night. What do I do to give it it's best chance to survive overnight and not inadvertently take it someplace they will just put it down anyway? Near a big tree so mother squirrel might be near, but guides say if bleeding to get it care rather than attempt to put it back by tree. Anyone here have more experience with this or know someone who does? Anyone local want to take it (we have cats, which I can keep away from it overnight, but still...)