PHOENIX - Earlier this week, Aaron Saucedo was formally charged in a string of killings that shook a Phoenix neighborhood last year.

He’s been behind bars since last April, indicted in another murder case. He pleaded not guilty to that charge.

According to police, the 23-year-old former city bus driver left behind bullet casings that forensically link him to the shootings.

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12 News spoke with the twin sister of one of the alleged victims.

Hearing the suspected shooter has been formally charged is bringing Horacio Peña’s twin sister, Nancy, a sense of peace.

”It was one of those moments where I really just wanted to fall to my knees,” she said.

It’s been more than a year now since her twin brother, 32-year old Horacio De Jesus Peña, was killed outside of his house after returning home from work.

“There was a rush of emotions, just you know, my whole – my entire life has changed since it happened,” said Peña, who continues to cope with the loss daily.

“Just reliving everything that I had to go through and what he might have gone through,” she said.

Saucedo is accused of pulling the trigger in a dozen random shootings in West Phoenix that left nine dead over the course of a year.

The fact Saucedo was formally charged is a big step in the healing process for Nancy. While she’s thankful, she said she knows she’ll have to stay strong to see the outcome of the case.

Peña said she wants Saucedo to know what he put her and so many other families through.

“Just know the pain that he caused,” she said.

Peña wants justice and plans to be there the day she hopes Saucedo is found guilty and sentenced.

“He will know that he messed with the wrong twin, unfortunately,” said Peña.

Until then, she’s working with people with disabilities at the same place her brother used to work, Valley Life in Phoenix. She now gets to hear what a difference her twin brother Horacio made in their lives. It has given her a new mission.

“Be the same kind of caregiver that he was,” she said, “just so humble and caring.”

Saucedo is behind bars on an $8 million-dollar bond and is due back in court July 6.

He entered a not guilty plea and told the judge during his arraignment last week, “I’m innocent.”