San Francisco police linked a man to dozens of spent shell casings from a shooting on April 4 in which no one was injured, and found in possession of a semi-automatic "ghost gun." The District Attorney's Office released him without charges, pending further evidence. He's now wanted for murder and attempted murder.

The SFPD made the rare move Tuesday night of releasing the mugshot of a man they suspect of killing two other men on Saturday, and attempting to kill one other. 32-year-old San Francisco resident Robert Newt, police say, is armed and dangerous. "If you see this individual do not approach him," the SFPD said on Twitter. "Note his location, clothing, and any vehicle description and immediately call 9-1-1."

Newt is at large and wanted for the May 15 murders of 61-year-old Darryl Haynes and 54-year-old Randy Armstrong. The fatal shootings occurred two and a half hours apart on Saturday — first, Haynes was gunned down near 25th and Connecticut streets just after 10 a.m., and at 12:30 p.m., Armstrong and another man were shot on Dakota Street less than a mile away — the other man remains hospitalized and was in critical condition as of Monday.

The motives and circumstances behind the killings remain unclear, but what is now clear is that Newt was in police custody just a few weeks ago in connection with an unrelated shooting. As the Chronicle reports, officers found over 30 spent shell casings from a semi-automatic weapon following reports of shots fired on the 1300 block of Quint Street on April 4. Witnesses say that a man, later identified as Newt, exited an SUV and fired at another man, who fled the scene and it was not known if he was injured. Newt was later pulled over for driving on the wrong side of the street on April 21, and officers allegedly found a semi-automatic "ghost gun" in his possession — an untraceable weapon assembled from parts purchased online.

The DA's Office says that his was a case in which there was insufficient evidence to prosecute Newt, and they were still waiting on fingerprint or DNA evidence that would more definitively connect him to the April 4 shooting.

In a statement to the Chronicle, DA's Office spokesperson Rachel Marshall says, "This is a common request when we need additional evidence to prove a case. It speaks to the need for developing faster testing processes so that we can more quickly charge cases that require forensic evidence."

But Saturday's homicides, if they turn out to be the work of Newt, add to a mounting docket of cases that feed into a narrative being pushed by proponents of an effort to recall DA Chesa Boudin. Since the start of the year, three vehicular homicides, a carjacking/kidnapping, and a double stabbing have been linked to individuals with criminal pasts — two of whom were very recently released from jail for dangerous and unlawful acts. Also, a report emerged in March about an accused sexual assault suspect who was arrested in one case last September, released with an ankle monitor, and implicated in another sexual assault in November.

The extent of Newt's criminal history is not yet known.

As KPIX reports, Newt is known to frequent the Bayview/Hunters Point area.

While the SFPD last year ended the practice of releasing pre-arrest mugshots of suspects in order to curb racial bias, they said they were doing so in this case due to the dangerous nature of the suspect.

Anyone with information about Newt's whereabouts is asked to contact the SFPD immediately by calling 911 or the tip line. People wishing to remain anonymous may call 415-575-4444 or they can text a tip to TIP411, beginning the text message with SFPD.