IMO, from the evidence posted so far there is no clear fault on Zimmerman except learning an armed neighborhood watch person should perhaps not pursue. Its more important an innocent man stay free, than let the guilty go free. The Lord is our final judgment.
I spent 20 years as a police officer. There are many times I prepared charging documents and an entire case file, but when I appeared before the prosecutor I recommended that charges not be filed. Almost always, the prosecutor would review the file, agree, and honor my request.
The mere existence of documents presented to the prosecutor in support of a manslaughter charge is meaningless.
Unless ABC News is prepared to quote Serino as saying "I really thought he should be charged with manslaughter", this report means nothing.