Baltimore Police Lt. Brian Rice, the highest ranking officer charged in the death of Freddie Gray, was on Monday acquitted on all counts.

It marks the fourth time prosecutors have failed to secure a conviction in the case, the Baltimore Sun notes, and in turn "is likely to renew calls for Baltimore State's Attorney Marilyn J. Mosby to drop the remaining charges[...] including from the union that represents the city's rank-and-file officers."

Rice was found not guilty of involuntary manslaughter, reckless endangerment, and misconduct in office by Circuit Judge Barry Williams in a bench trial. Williams previously handed down acquittals for officers Caesar Goodson and Edward Nero. The trial for Officer William G. Porter ended with a hung jury in December. A retrial is set for September 6.

The Sun reports of Williams' verdict on Monday:

The prosecution did not show Rice acted in a "grossly negligent manner," required of manslaughter, he said. It did not show that Rice acted in an unreasonable way or ignored the substantial risk in placing Gray in a police van without a seat belt, required for reckless endangerment, he said. And, it did not show Rice acted "corruptly," which is required for misconduct in office, he said.

Williams said a "mistake" or an "error in judgment" by Rice was not enough to prove the crimes alleged. He also briefly noted the difference between criminal negligence and civil negligence, an apparent nod to the fact that the city previously negotiated with Gray's family attorney, William H. "Billy" Murphy, on the civil side and agreed to pay the family $6.4 million.

According to Baltimore Sun crime reporter Justin Fenton, "the scene outside of the courthouse is very calm."

But some voiced their frustration on social media:

So #FreddieGray's death was ruled a homicide, right? But none of the officers involved killed him? Who are they charging next?--the van?

— Jacqui G. (@jaykayG) July 18, 2016

I get the depraved-heart murder charge was always an overreach. But how the hell were they acquitted of reckless endangerment? #FreddieGray

— Matthew Chapman (@fawfulfan) July 18, 2016

Yet another officer found not guilty in the death of #FreddieGray. The whole thing is a huge debacle.

— Shaun King (@ShaunKing) July 18, 2016

There are two officers still facing charges. Officer Garrett Miller is scheduled to go to trial later this month and Sgt. Alicia White heads to court in October.