"He was the love of my life. We had a special kind of something," Cagle said. "He was the best father. And I wanted to spend the rest of my life with him. But now I don't have that chance."
She said she'll continue to wear the ring "for a long time," and hopes to help get justice for her fiancé.
Kenneth White, 32, was killed just north of Flint, Michigan, on October 18 while riding in a car that was hit by a rock thrown from a highway overpass. Police say five teens threw a series of rocks from the overpass and then went to eat at a McDonald's.
The five have been charged with second-degree murder, all accused of playing roles in throwing the deadly rock. Kyle Anger, 17; Alexzander Miller, 15; Mark Sekelsky, 16; Mikadyn Payne, 16; and Trevor Gray, 15, were arraigned Tuesday and pleaded not guilty, according to Gray's attorney, Erwin Meiers.
Cagle said she plans to go to as many court dates as she can.
"I want people to know about this," Cagle said. "I want people to know that there are consequences for your actions."
But proving the five teens knew that hurling a 6-8 pound rock from a highway overpass at cars going about 70 mph could result in someone's death could be difficult for Genesee County Prosecutor David Leyton, who is trying all five teens as adults.
White was riding in the passenger side of a van, heading home from work, and died shortly after the rock came through the windshield and hit him in the chest and face.
"The injuries are horrific. ... I gasped out (when I saw them.)" Leyton said. "I've seen a lot in four terms."
Leyton said he believes the teens should have known that throwing rocks from a highway overpass could cause bodily harm.
"I think they wanted to throw rocks down on the highway and hit vehicles as those vehicles came by," Leyton said. "I don't think they said, 'OK, we're going to kill Kenneth White when he comes hurtling down the road.' But I do think they said, 'We are going to throw a rock down at the next car that goes by and try to hit it.'"
It's an especially difficult case for Leyton to prosecute. His office is filled with photos of his four children, who are similar in age to the accused teens. He used to officiate football games at Clio High School, where the five accused teens were enrolled.
"My heart hurt when I had to make the decision. Because ... they're kids," Leyton said. "And when they were marched into that courtroom the other day for their arraignment and I looked at them ... some of them are even younger than they appear on paper. When you read the reports, it's -- they sound like adults, but when you see them, they're clearly children."
Frank Manley, an attorney representing Sekelsky, said he believes his client's case should eventually move to the juvenile justice system.
"I know people will come back and say they're not children, they're monsters -- really they're not," Manley said. "They're children, and nobody -- even the prosecutor -- would agree they meant to kill."
The lawyer for Payne, Mike Manley, said he knows the case has generated anger.
"I understand the outrage. I understand there needs to be justice and accountability. But we can't let our emotion and anger take over," said Manley, who is Frank Manley's brother.
"It's time for the grownups to get together. I am talking about the attorneys and law enforcement. We have to come up with solutions that benefit society and these children," he said.
On Tuesday, Gray's attorney, Meiers, said, "You've got five children charged with offenses carrying life in prison. One minute they're looking to going to prom or homecoming and the next minute they're sitting in a detention center."
Attorneys representing Anger and Miller did not immediately respond to requests for comment.
Leyton said his office will be looking through the teens' school records this week, sifting through disciplinary records and transcripts. They will look through the teens' text messages and social media accounts. They also are sending rocks from a pile near the overpass to the Michigan State Police crime lab, in an effort to show where the rock that killed White came from.