The sad and bizarre case of the random shooting of a San Francisco woman by a transient Mexican man in the US without documentation has taken an even stranger twist, at the news that the gun used in the shooting might have belonged to an agent with the U.S. Bureau of Land Management.

You know the details of the case by now: 32-year-old Kate Steinle was strolling on Pier 14 with her dad last Wednesday when she was shot dead. 45-year-old Francisco Sanchez, who had been deported from the US five times, admitted to the shooting, saying that he'd found the gun on the ground, wrapped in a t-shirt. He appeared in court Wednesday with his public defender, former SF Supervisor Matt Gonzalez, where he pleaded not guilty — but the news of his perplexing (in the light of his televised confession) plea was dwarfed by the shocking revelation that the killer weapon wasn't just any gun, it was a gun that belonged to a federal agent.

First reported by ABC7, anonymous sources have since confirmed to any number of news organizations that forensic experts traced the gun back to a federal agent. According to an Associated Press report from Wednesday, that agency is likely the U.S. Bureau of Land Management, which says that they are trying to determine "who owned the gun and whether it was a personal or service weapon."

San Francisco Police Chief Greg Suhr tells the AP that "the weapon was stolen from a federal agent's car," after "a car burglary in San Francisco in late June," the Chron quotes an anonymous source as saying.

"Other sources said the weapon — which Lopez-Sanchez allegedly dumped in the bay before it was recovered — was apparently not the agent’s official gun," reports the Chron. According to KRON4, the weapon in question is a 40-caliber Sig Sauer pistol "that was recovered by a police dive team in the bay last Thursday...The source described the weapon as being an expensive, high-end, common police gun."

While the BLM figures that one out, we can cast our attention back to Sanchez's Wednesday's court appearance. As you know, this case has attracted international attention around the hot-button topic of immigration into the US and San Francisco's Sanctuary City policy. As a result, the courtroom was mobbed Wednesday as Judge Daniel Flores read the charges against Sanchez as Gonzalez stood by his side, charges to which Sanchez responded “no culpable."

In addition, KQED reports that "twice during his arraignment Sanchez told the judge in English, 'I’m not guilty,' although the judge had already heard his plea and was asking him an unrelated question regarding scheduling."

But what about the interview with ABC7 in which Sanchez admitted to the crime? It might not be that simple, Public Defender Jeff Adachi said outside the courtroom.

"That interview was done primarily in English by a reporter," Adachi said.

"I think certainly, that interview raised a lot of questions about whether Mr. Sanchez understood what was being asked.”

Gonzalez said Wednesday that “this very well could be a completely accidental discharge of a firearm...You’ve got an individual who does not know the victim in the case, has no interest or desire in injuring her in any way, and no witness or anybody to allege that there was any crime going on at the time the shooting occurred.”

San Francisco Assistant District Attorney Alex Bastian tells KRON4, however, that “we’ve charged this case as murder and we do so based on the evidence. And at this point, the charges are appropriate.”

Unlike the San Francisco Police Department's union, the DA's office does not appear to welcome the immigration debate into the prosecution of the homicide. When the Chron asked Bastian how Sanchez's status as an undocumented immigrant played into the case, Bastian, "demurred and said, 'today’s about Kate.'"

“It’s about this incredible family that has shown such strength during this incredibly difficult time...It’s about bringing justice to that family and it’s about doing everything we ethically can to prosecute this case and bring the justice this family rightfully deserves.”

Sanchez, who has been charged with one count of murder with enhancements for the use of a firearm, remains in San Francisco County Jail on $5 million bail. He is expected to return to court on July 27.

Previously: Police Say Woman Killed Next To Ferry Building Might Have Been Random Victim Of Attack
Video: 'Wandering' Man Says He Took Sleeping Pills From Dumpster Then Shot Woman At SF Tourist Attraction
SF Police Union Lashes Out At 'Elected Official' Over Kate Steinle Shooting Death