CHICAGO (CBS) — Her tragedy made the headlines this fall, when Cassandra Tanner Miller’s estranged husband shot killed their 1 ½-year-old son, Colton Michael Miller, and then himself.

It was a gruesome murder suicide that should have been prevented. CBS 2 Investigator Megan Hickey is uncovering why it happened, and how Cassandra is working to change her future.

On Sept. 21, 2019, Cassandra was home with her 9-year-old daughter, Camryn, and her 18-month-old son, Colton. She had just put down Colton for a nap. When she turned around, she saw her estranged husband in the door from the back porch into their kitchen.

“He just said ‘Are you all ready to die today?’ with this big smile on his face; and I just screamed, ‘Cam, please go get your brother. Don’t stop for anything,’” Cassandra said.

Cassandra Tanner Miller had just put her 18-month-old son, Colton, down for a nap on Sept. 21, 2019, when her estranged husband forced his way into her house, severely beat her, and killed Colton before taking his own life. (Credit: CBS)

Cassandra said the details of what her estranged husband did that day are important for people to hear.

Christopher Michael Miller, 35, a former corrections officer and member of the Illinois National Guard, severely beat and strangled Cassandra until she lost consciousness.

“He dragged me by my hair,” she said. “I was trying to grab things, see if I could get him to slow down.”

After beating Cassandra, Christopher went up the stairs to the master bedroom, where Colton was sleeping.

Christopher shot and killed him.

“How could you do that to your baby?” Cassandra asked.

Colton Michael Miller was 18 months old when his father, Christopher Michael Miller, shot and killed him on Sept. 21, 2019. His father also took his own life, after brutally beating his estranged wife, Cassandra Tanner Miller, and beating their 9-year-old daughter, Camryn. (Photo supplied to CBS)

Christopher then beat and choked their daughter in the upstairs bathroom. When he saw Cassandra coming up the stairs, he let his daughter go, and fired shots at Cassandra and Camryn, who ran out of the house.

Moments later, Christopher shot and killed himself.

Cassandra did everything she was supposed to do to protect herself and her children from Christopher after they separated. She said law enforcement, the Illinois National Guard, and the judicial system all let her down.

Christopher shouldn’t have had a gun. His FOID card was revoked in January 2018 for an aggravated battery charge in DuPage County.

Illinois State Police sent out a letter notifying Christopher he was required to surrender his gun, but he never did.

Cassandra also sounded the alarm to the Illinois National Guard, reporting his violent behavior and drug use.

“That he was hearing things, that he wasn’t being responsive the way that he should, and I was just pretty much told to mind my own business and they kind of just stopped answering my phone calls,” she said.

Colton Michael Miller, a former corrections officer and member of the Illinois National Guard, had his FOID card revoked in January 2019, eight months before he shot and killed his 18-month-old son, Colton, and took his own life. (Photo supplied to CBS)

An Illinois National Guard Spokesperson said they’re investigating the way they handled her calls.

Illinois State Rep. David Welter (R-Morris) said the courts also failed her.

“She’s opened up my eyes, I think, to a different way of thinking about domestic violence,” Welter said.

Welter said he is currently working on legislation to enhance the option to put violent offenders like Miller on a GPS alert system. He’s calling it Colton’s Law.

Cassandra started a group called Colton’s Legacy, and she’s hoping to expand her teaching program across the state.

“I just wanted him to be proud of me that I was honoring him the right way that a mother should, you know?” Cassandra said.

Colton Michael Miller was 18 months old when his father, Christopher Michael Miller, shot and killed him on Sept. 21, 2019. His father also took his own life, after brutally beating his estranged wife, Cassandra Tanner Miller, and beating their 9-year-old daughter, Camryn. (Photo supplied to CBS)

Meanwhile, Welter plans to introduce Colton’s Law in the Illinois House later this month.

Illinois State Police said they’re still working on getting us the updated numbers for how many people are actually turning in their FOID cards. Our request has been pending for a month.

Megan Hickey