A San Mateo County judge on Tuesday dismissed murder charges against a man suspected of fatally shooting East Palo activist David Lewis in San Mateo in 2010, ruling that police had inappropriately obtained a confession, the district attorney said.

Gregory Elarms, 60, has been accused of following Lewis to the Hillsdale Shopping Center on June 9, 2010, where he allegedly shot the man once in the stomach with a .44-caliber handgun, fatally wounding him, according to the district attorney's office.

Six months after the killing, an anonymous caller in Pittsburg contacted investigators at the San Mateo County Police Department and claimed he had information regarding Lewis' murderers, according to police.

The caller, who turned out to be Gregory Elarms, allegedly said he needed protection because Lewis' killers had been threatening him.

District Attorney Steve Wagstaffe said that detectives offered to meet with Elarms. While he was in police custody but before he was arrested, the suspect allegedly confessed to the murder and "muttered" something about needing an attorney.

When Judge Stephen Hall dismissed the murder charge and a related gun charge on Tuesday, he ruled that the confession -- a key piece of evidence in the case -- was inappropriately obtained, and that Elarms' Miranda Rights had been violated, Wagstaffe said.

"While we respect the judge's ruling, we believe it is erroneous," he said.

He said the district attorney's office will be reviewing the case and possible options for moving forward, such as appealing the judge's decision or re-filing murder charges.

The murder holds particular interest to the community because of Lewis' decades of work in East Palo Alto and the Bay Area, advocating for "the downtrodden" and working to reintegrate former inmates and parolees into productive roles in society, Wagstaffe said.

"We have to do everything in our power to make sure Mr. Elarms faces justice," he said.

Elarms, who had been ruled incompetent to stand trial until earlier this year, was still in custody without bail at San Mateo County jail after the judge’s decision, Wagstaffe said.

He was still facing a weapons charge for being found with an illegal sharp object while in custody, Wagstaffe said.

A hearing on how to proceed with that charge was scheduled to take place in Redwood City on Tuesday.