SAN FRANCISCO (AP) — Three tourists visiting San Francisco two years ago testified Tuesday that they saw a man — now charged with murder — on a popular pier moments after hearing a gunshot that killed a woman and reignited the national debate over illegal immigration.

All three witnesses were called to testify on the second day of the trial of Jose Ines Garcia Zarate, a Mexican national who was arrested an hour after 32-year-old Kate Steinle was shot and killed on July 1, 2015, while walking with her father and a family friend.

Authorities say Garcia Zarate had been deported five times and was recently released from jail before the shooting.

Marie Moreno and Aryn Carpenter, roommates who live in California's Central Valley, were spending that night in a hotel overlooking the pier. They both testified that they heard the gunshot and ran to a window where they saw Garcia Zarate walking quickly from the pier.

They said he stood out because nearly everyone else was either looking around confused or running toward an adult who was down on the pier.

"He had a scowl on his face," Moreno testified.

They said a woman who was walking away appeared to be calling 911.

Trial is underway in San Francisco for a Mexican national accused of murder in the death of Kate Steinle. The 2015 shooting sparked a national debate over crime and illegal immigration. (Oct. 24)

Garcia Zarate has told police that he shot Steinle, but it was an accident that occurred when he picked up a T-shirt under a bench that was wrapped around the gun and it went off.

Prosecutors have charged him with murder and say he pointed the gun at Steinle and pulled the trigger.

"This case boils down to one baseline question," San Francisco district attorney's spokesman Alex Bastian said outside court. "Whether or not the defendant pulled the trigger."

Earlier in the day, Michelle Lo testified about walking past Garcia Zarate as he sat on a swivel chair on the pier. She took three photos that showed him sitting on the seat and the back of Kate Steinle several yards (meters) away, moments before she was shot. The photos were shown to the jury.

Steinle's death sparked debate over illegal immigration and sanctuary cities such as San Francisco that limit interaction between police and immigration authorities.

Garcia Zarate was homeless when he shot Steinle. He had recently completed a prison sentence for illegal re-entry to the U.S. when he was transferred to the San Francisco County jail to face a 20-year-old marijuana charge.

Prosecutors dropped that charge, and the San Francisco sheriff released Garcia Zarate from jail despite a federal immigration request to detain him for at least two more days for deportation.

The handgun fired in the killing belonged to a U.S. Bureau of Land Management ranger who reported that it had been stolen from his parked car a week before Steinle was shot.

Garcia Zarate, 54, is charged with second-degree murder and could face a sentence of 15 years to life in prison if convicted.

The judge in the case has prohibited any mention of the politics of immigration and gun control during the trial that is expected to last several weeks.

Trial continues Wednesday.