Story highlights

Hamilton was shot more than a dozen times by Christopher Manney in April 2014

Officer has said he opened fire when Hamilton grabbed his baton and struck him with it

Attorney for Hamilton's family says civil rights lawsuit in federal court is now "last resort"

CNN  — 

Federal officials announced on Tuesday that they had closed their review into the shooting death of Dontre Hamilton, finding insufficient evidence to pursue federal criminal civil rights charges against the former Milwaukee police officer who shot him.

Hamilton was shot more than a dozen times by then-Officer Christopher Manney in April 2014. Manney has said he opened fire when Hamilton, who was mentally ill, grabbed his baton and struck him with it.

“In this case, there were numerous civilian witnesses who saw some part of the physical confrontation between Manney and Hamilton. Based on those eyewitness accounts, the account of the former officer involved, the physical evidence and the assessments of independent use of force experts, the team of experienced federal prosecutors and FBI agents determined that the evidence was insufficient to prove, beyond a reasonable doubt, that Manney acted willfully with a bad purpose to violate the law,” the Justice Department said in statement.

“Accordingly, the federal review of this incident has been closed without prosecution,” it read.

Last year, a district attorney similarly decided not to pursue criminal charges against Manney, who was fired for not following protocols.

Lawyers for Hamilton’s family said they were disappointed by the federal government’s decision, and vowed further action.

“Now that the potential criminal reviews have been conducted by the state and federal governments, the last resort is a civil rights lawsuit to be filed in federal court, which we are prepared to pursue,” attorney Jonathan Safran told reporters.