One shot hit Zarate in the neck, killing him. He died in the parking lot. He was 39.
A woman riding in the car with him was hit by shrapnel or flying glass, police said, and was injured.
A stray bullet also flew through the Walmart parking lot, wounding a third woman who "wasn't involved at all," McManus said. Both women are expected to recover.
Police identified the suspect as Teles Mandan Juarez, 21.
Juarez sped away from the scene but was pursued by the police department's helicopter. Police arrested him about 10 miles from the Walmart.
He was charged with aggravated assault and retaliation, both felonies. He could also face a murder charge.
Meanwhile, Zarate's wife, Lisa Benavides, was oblivious to what was going on outside the crowded store.
Her mother had wanted to go to San Antonio's annual public lighting of the River Walk for the holidays. But Benavides wanted to get a new outfit for the occasion, so they braved Black Friday crowds to make a Walmart run.
She promised to hurry as her husband circled the packed parking lot.
She quickly found an outfit, raced through the self-checkout "because it was fastest," and stood at the curb with her bag. She waited in the parking lot for the family's Toyota Camry to pull up.
Instead, she saw police cars.
Curious, she inched closer to the police tape, but officers and their vehicles obscured her view.
"I asked a man standing nearby what happened and they said someone got shot," she said. "I asked if that was a Toyota Camry and when the cars moved, the man could see and he said 'yes.'
"I knew right then it was my car. I started running. And I went underneath the line and they said, 'You can't go back there,' and one of the cops grabbed me and said, "Who are you?' "
"I said 'That's my husband.' "
Through tears on Sunday morning, Benavides told The Washington Post that she was shocked by the outburst of violence that took her husband's life, but not surprised that his final act was to help someone.
She recalled a Teddy bear of a man who was quick to give spare change or leftover food to homeless people.
They'd both grown up poor, and empathized with people who were struggling.
Zarate was a childhood friend of Benavides's brother. For years, he harbored a crush on the woman who would become his wife, but she'd tell him, "Get out of my house and stop eating my food."
She was won over by his kindness, especially by the way he was protective of her when she was a new mother and her relationship with her baby's father fizzled.
"He raised my oldest son since he was 8 months old," she said. "He raised him like his own, even though [the child's] father wasn't in the picture."
They went on to have three more boys. Their sons are now 17, 19, 20 and 23.
Zarate was the jokester in their family - a storyteller prone to spin a tale when only a "yes" or a "no" was required. She always told him to get to the point. He needled her about taking too long at the store.
Beneath it all, he encouraged his family to be kind.
"He's always been like that," Benavides said. "Even though people treat you mean, he said you've always got to be nice. And he always said you've got to help people in the long run. It's going to all come back to you."
The family is planning a funeral for Zarate, and has set up a GoFundMe page to cover expenses. The fund was nearing its $20,000 goal Sunday afternoon.
For Benavides, her husband's funeral will be the first big thing she has undertaken on her own in 22 years.
"I don't know what I'm going to do without him because we were together 24/7," she said, crying. "We've always been together. I can't believe he's gone.
