24-year-old accused of attacking grandfather and watching indifferently

An Arizona woman shot and killed a 54-year-old man with a bullet to the neck during a road rage confrontation, claiming "he confronted me" and spat on her, according to witnesses and authorities. 

She is said to have returned to her vehicle after the incident and observed the man bleed out as if she "didn't care" about his condition, witnesses report.

Legal filings reviewed by Law&Crime accuse Heather Arriaga, 24, of fatally injuring Stephen Guardino in September 2025 during a road rage clash in Phoenix.

"It was a shocking scene," witness Isaiah Cline mentioned to the local news source AZ Family.

"She remained in her car as he was just there dying," added another witness, Brody Madrid. "Didn't care."

Arriaga turned herself in to Phoenix Police headquarters on Monday evening and "voluntarily surrendered" to officers around 6pm after a manslaughter warrant was issued, according to the documents.

Eyewitnesses told AZ Family following the incident that Arriaga and Guardino stopped at a red light near the crossroads of 7th and Missouri Avenues, south of Bethany Home Road, when the altercation occurred across from a Starbucks on September 27, 2025. Arriaga supposedly fired at Guardino while seated in her car.

"They were more or less trying to merge into each other's lanes, following each other very closely," stated witness Malasia Williams. "He spat on her, and she shot him."

People present and witnessing the incident rushed to provide assistance, according to police and bystanders, while Arriaga allegedly did nothing to assist.

"She said, 'I shot him. I'm sorry. He approached my car. I was frightened. He confronted me, I shot him,'" witness Isaiah Cline reported to AZ Family.

"I did my best [to help] and left it in God's care," said Madrid.

An online memorial notice for Guardino describes how he was "tragically taken … in a needless road rage altercation." 

He was affectionately known as "Tata Steve" and had grandchildren through his stepsons, the notice reveals.

"Steve will always be remembered for his wit, intelligence, creativity, and generosity," the memorial notice states. "He will be sorely missed."

Arriaga’s arraignment is slated for April 14.