Updated

The fourth day in the trial of the homeless illegal immigrant charged with killing Kate Steinle featured testimony from a government employee whose gun was stolen and used in the shooting.

Agent John Woychowski Jr. took the stand Thursday in the trial of Jose Ines Garcia Zarate, who's charged with killing Steinle on July 1, 2015 on Pier 14 in San Francisco. Woychowski works for the Bureau of Land Management and was issued a company weapon.

On the day of the shooting, Woychowski, who was off duty, said he and his family were on their way to Montana and stopped in San Francisco for dinner. He told the jury he parked his car in what he thought was a safe location and left a black backpack, which had his loaded weapon inside, in the back seat. He said the car was locked and had an alarm and tinted windows.

When his family returned from dinner, he said his car's windows were smashed and the backpack was gone.

He said he immediately reported the theft to 9-1-1 and his employer.

COURTROOM GASPS AS VIDEO OF KATE STEINLE'S SHOOTING IS PLAYED FOR JURY

Prosecution brought out a P239 weapon as evidence which Woychowski confirmed was his and showed the jury how it worked, adding that he'd never had trouble with it.

Defense attorney Matt Gonzalez cross-examined the agent, focusing primarily on why the agent had a loaded gun if he was off duty -- and why he left it in the car.

Woychowski said he was required to keep his weapon loaded in a specific way and reiterated that he thought the car was safe. He said he always kept the backpack on him to protect his family.

He added that his employer had issued a locking device for the gun but he didn't have it on him that day and that the gun did not have an external safety.

Woychowski told the jury that he was unaware of any of his co-workers with the same type of gun reporting instances where it went off on its own.

Next on the stand was San Francisco Police Department Officer Andrew Clifford, who responded to the scene on the pier. Clifford was the officer who conducted the gunshot residue test on the suspect. The test was submitted to the court as evidence and passed around to the jury.

The final witness of the day was Linda Avuan of the SFPD crime lab who testified that Zarate's right hand tested positive for gun shot residue. She told the jury that even with a single particle of residue, like the one on Zarate's hand, the test result is still positive -- quantity of samples does not matter.

During Wednesday proceedings, SFPD Officer Craig Dong took the stand. He was expected to resume his testimony on Thursday but ultimately did not appear in court and both sides said they had concluded their questioning.

Dong was on the scene on the day of the shooting and worked on enhancing video from a nearby fire station that appeared to capture video of Zarate and also Steinle and her father at the moment of shooting.

During his testimony, jurors saw a video that showed Steinle falling, the suspect walking away and something splashing in the water.

When the part of the video showing Steinle was played, people in the gallery of the court room could be heard gasping. The video was played back again, during which an alternate juror stood to get a second look.

Members of the victim's family have not been seen in court since Tuesday.

Previous days in court have included testimony from witnesses on the scene and responding officers who handled evidence and investigation.

KATE STEINLE TRIAL FEATURES TESTIMONY OF WITNESS TO KILLING BY ILLEGAL IMMIGRANT

Zarate, 54, admitted shooting Steinle, but says it was an accident.

Steinle's father testified Monday that before she died, she said to him: "Help me, Dad."

The prosecution said those were her last words.

While Garcia's immigration status is what brought the case into the national spotlight, jurors will not hear evidence about that, and it will not be a factor in the trial.

Steinle's slaying became a signature issue for Donald Trump as he was running for president. He invoked the slaying in calling for the construction of a wall on the Mexican border and stepping up deportations and cracking down on illegal immigration.

Fox News' Michael Lundin in San Francisco contributed to this report.