CBS News has learned the alleged Golden State Killer will be charged Monday for what investigators believe was his very first murder. Joseph DeAngelo is accused of shooting Claude Snelling in Visalia, California, in 1975. The district attorney and police chief will announce the new charges. Detectives say his criminal behavior escalated in the small farming town, from sadistic burglar to notorious serial killer.

Elizabeth Hupp CBS News

"In my heart, I believe he's the one, and that my father was his first victim," Snelling's daughter, Elizabeth Hupp, told "CBS This Morning." Her father gave up his life to save her from being abducted by the so-called "Visalia Ransacker," reports CBS News correspondent DeMarco Morgan.

In September 1975, she said a masked gunman broke into her bedroom in the middle of the night, threatened her, and then dragged her out to their carport.

"That's when I heard my dad yell and… the man with a ski mask pushed me to the ground, turned, and shot my dad twice as he was coming through the back door," Hupp said.

Snelling died on the way to the hospital. Hupp was 17 years old at the time.

"He's always been my hero," Hupp said, adding, "I would not be here today, I'm sure of it, if it hadn't been for him."

Tulare County district attorney Tim Ward believes Snelling was the first victim murdered by Joseph DeAngelo, the suspected Golden State Killer.

"We're filing first degree murder charges against Mr. DeAngelo, along with an allegation that he used a firearm in the commission of that murder," Ward said.

During the 1970s and '80s, DeAngelo allegedly committed at least 12 other murders and more than 50 rapes in 10 California counties. DNA evidence lead to his arrest in April.

While DeAngelo is not directly linked to Snelling's murder by DNA, police chief Jason Salazar said he can prove DeAngelo is also the Visalia Ransacker.

"We have been able to locate victims and witnesses that were able to identify Mr. DeAngelo as the suspect back in that time," Salazar said, adding, "Those crimes were ultimately tied to the murder of Claude Snelling by a firearm that was taken from one of the Ransacker burglaries."

At the time of Snelling's murder, DeAngelo worked as a police officer about 12 miles away in the town of Exeter. He is also suspected in about 100 burglaries and attempted sex assaults in Visalia.

"The only crime that we can attribute to Mr. DeAngelo that has not passed the statute of limitations is the murder of Mr. Snelling," Ward said.

DeAngelo has not yet entered a plea in his criminal cases.

"I'm just very happy that he's caught," Hupp said. "He's a very evil person."

The Visalia Ransacker was nearly captured three months after Snelling's murder. He managed to escape after firing a gun at a detective who tried to arrest him. Shortly after that, investigators believe he moved to the Sacramento area, beginning a new crime wave as the East Area Rapist.