The father of an infant killed in a triple murder-suicide last year in Verdigris, involving two other children under 11, says his purpose is growing stronger after going to Oklahoma City on Thursday for a ceremonial signing of the Three Angels Law. 

Lawmakers passed it to prevent a tragedy like this from happening again.

When Billy Jacobson first learned his son, Billy Jr., and two other kids were murdered by their mom, Brandy McCain, Billy Senior felt like it was all nothing. 

Now he says because of this bill, those three kids have a legacy. 

Jacobson says pushing through the murders of his son and two other children felt impossible, but he says he knew he had no other choice because he has two daughters at home. 

"I had to come up with some way for me to be able to make it through day to day to still be there for them, and the only thing that came to my mind was to blast this as loud as I could and make change in any way I possibly could," he said.

Jacobson decided he was going to make it his mission to change child custody and visitation laws to keep kids safe.

"Now they have to do a full mental health assessment, and it has to be signed off on by a professional before they allow you to get your children," said Jacobson.

Jacobson says that could have prevented his son's death because he says McCaslin had a mental health crisis months before she killed the kids and then killed herself.

"We have made changes in the bill to where if you have a suicide attempt, violent act, or drugs that you will have to be in a supervised environment, a professional environment, to do visitation," said Jacobson. 

On Thursday, Jacobson went to the Oklahoma State Capital for a ceremonial signing of the Three Angels Law.

"I was choking back the tears most of the time; it was overwhelming seeing the support we had," said Jacobson.

Jacobson says his son's time on earth was short, but Billy Jr., Noe, and Bryce will make a difference in thousands of families' lives. 

"In the end, my little 9-month-old son will have done more in his 9 months than I will have in, as of this month, 43 years," Jacobson said.

Three Angels Law will go into effect on November 1.

Jacobson says he hopes to bring these changes to Washington, D.C.