A man who was driving a car in which a woman was shot to death is being held on $1 million bail, but it was still not clear by press time exactly who shot her.

Killed in the altercation was 21-year-old single mother Erica Hindman of Pasadena, who was traveling in a car driven by Walter Villanueva, 23.

Villanueva allegedly opened fire outside of a party early Sunday morning near a home at the corner of Tremont Street and North Marengo Avenue when he was spotted by officers. Police were already at the scene investigating previous complaints made about Villanueva, who witnesses said had been at the party earlier.

Police are trying to determine if Villanueva or first-year Officer Timothy Bundy, 30, fired the fatal round.

“This is a horrific incident,” said Police Chief Bernard Melekian. “Walter Villanueva started a chain of events that terrorized members of this community and they led to the tragic death of Erica. The Pasadena Police Department grieves for her and with her family during this difficult time.”

Even if Bundy fired the shot that killed Hindman, Villanueva is still culpable for her death, according to state law, which holds that a suspect can be charged with murder if someone dies during the commission of a felony.