After Journalist Daughter's On-Air Shooting Death, Dad's Book Is 'Call to Action' on Gun Violence

Andy Parker was a doting father, and he remembers countless small moments he shared with daughter Alison Parker while she was growing up.

He vividly recalls the first time he took her trick or treating. He remembers the time when, at 6, Alison went to an amusement park and got spooked and she jumped into his arms. He took pride in being her protector.

Things were no different when Alison grew up to be an Emmy Award-winning TV reporter. Parker delighted in hearing every detail of the stories she was working on and her many plans for the future.

All of that was stolen from Parker and his family on August 26, 2015, when Alison was fatally shot at age 24 during a live, early morning interview for CBS affiliate WDBJ.

In the aftermath, Parker, now 65, couldn’t stop thinking how he hadn’t been there to protect her when she needed him most.

“I worshipped her,” Parker tells PEOPLE. “She was the light of my life.”

He can’t bring back the daughter he adored, he says. What he can do is honor her memory by fighting to end gun violence in America — and he writes about his mission in his new book, For Alison: The Murder of a Young Journalist and a Father’s Fight for Gun Safety.

The book, which hits bookstores today and was published by Apollo Publishers, is “part memoir, part current affairs and also a call to action,” he says.

For Alison details the horrific day she was murdered on-air at Virginia’s Bridgewater Plaza, where the Parkers had happily spent summers past, and his journey to becoming one of the most outspoken voices of the gun violence prevention movement.

“Writing this is something I felt compelled to do,” says Parker, who worked in the banking industry before becoming a full-time advocate. “I felt like I had to do it for the people who have lost their lives to gun violence and most importantly, I had to do it for Alison. I needed to tell her story.”

On that fateful morning, viewers watched in horror as disgruntled ex-reporter Vester Flanagan, 41, who was also known as Bryce Williams and had worked at the station where Alison was fast becoming a star, pulled a gun on her and her cameraman, Adam Ward, 27. Alison and Ward died in the shooting, and a local chamber of commerce head Alison was interviewing at the time was injured.

Hours later, the gunman uploaded to the internet video footage of the slayings he’d filmed with a Go-Pro camera. He later fatally shot himself.

Besides tearing a hole in his heart, Alison’s murder ignited a fury inside Parker that is fueling his fight to keep others safe.

Ever since the day Alison died, “I vowed to spend the rest of my life doing whatever it takes to prevent this from ever happening to another family,” he says.

As he has said in past interviews, Parker makes it clear in the book that his aim is not to take anyone’s guns away.

“I just want common-sense gun legislation,” he says.

This includes universal background checks on gun purchases and transfers and closing gun show and online ordering loopholes, he says.

Though more than 3 years have passed since Parker lost his daughter, the pain remains. “It’s never going away,” he says. “Some days you feel worse than others. There’s a void there that you can never fill.”