Should we enter Syria's conflict?

I had promised myself not to speak about Syria's conflict here, but the truth is, I cannot keep from doing so.
Over 70 thousand people dead and now there is evidences of chemical weapons being used and obviously affecting civilians.
Do we know who used it?
I don't.
Who can tell me without a shadow of a doubt that it wasn't the rebels doing so, to make us help them in their cause?
This isn't to say their's is the wrong side for I am always in favour of ending oppression agaisnt autocratic governments, however I believe it should be that country's people fighting for their freedom and outsiders should intervene only as a last recourse.
I do hope the rebels had nothing to do with these weapons' use since it would mean they are starting with the wrong foot on their road to reach that so expected freedom as actions like these only show that  whoever did it has no boundaries nor respect for human life.
So do I think it is time for our intervention?
 Yes I do.
I think everyone who values human beings lives thinks these way since too many people have died already for us ignore what is going on. Remember inaction is as reproachable as some actions.
Yet, I believe it shouldn't be one country's decision.
 I've always thought that the UN's organization was created to prevent another genocide like the one which happened on WWII from happening again so I think it should be on them to decide helping those people without waiting for a decision from US's government.
One country alone should never have to have that burden on its shoulders, this should be a join decision taking into consideration that it shouldn't take long to decide for human lives are being lost in the process.