SANTA ANA, CA — The former cop suspected of being the Golden State Killer probably got away with murdering 12 people and raping 51 women for so many years because of his background in fighting crime, said an Orange County Sheriff's investigator who worked the case for decades.

Investigator Larry Pool said he felt "mixed emotions" Wednesday about the arrest of the suspected Golden State Killer, a case he has worked on for 20 years. The case that culminated in Tuesday's arrest of Joseph James DeAngelo, 72, was Pool's first case. "In 1998, I was assigned to sex crimes," Pool said. "It was my first investigation assignment."

Pool said his boss "seemed to think I was the right fit -- and he always knew of my interest in serial offenses." Also, Pool said, he was "aspiring to become a homicide investigator."

So, how did he feel when he got the call his suspect was handcuffed? "Mixed emotions," he told City News Service. "Elation, a sense of relief that I have not had felt the depth of in a good 20 years. Satisfaction and also a sense that our work has just begun. There's a lot of work behind us and a lot of work ahead of us."

Pool "rejoiced" when he heard a suspect was behind bars.

"It felt great," he said. "It's a feeling I've been longing for for 20 years."

But he said he also felt "stunned." "When it does happen it takes your breath away a little bit," he said. "I'm still experiencing what the survivors are experiencing -- that we'll wake up tomorrow and pinch ourselves -- is it real?"