He, she or they knew that the current system is rotten to the core. Any person being a real threat to the current system will be taken out, be it friendly or deadly. 

Better to stay anonymous after kicking the hornets nest. 

Too bad people are searching for the identity. 

 So, mostly fear of the government 

 I don’t think it’s specifically the government. Might be some other forces who don’t want to lose control. Governments are just puppet shows 😉