ST. PETERSBURG, Fla. (AP) — A man who pleaded guilty this month to killing a pregnant Florida teenager a decade ago has been sentenced to 40 years in prison after sending authorities to dig up a field in rural Alabama in a fruitless search for her body.

Jacobee Flowers, 34, would have received a lighter sentence of 25 years in prison if the remains of Morgan Martin, 17, had been found, the Tampa Bay Times reported. He had told authorities in Pike County, Alabama, where to look in their unsuccessful search earlier this month.

Flowers, the father of Martin’s unborn child, was taken into custody on Tuesday, and apologized for his actions during his sentencing on Thursday.

“I want you all to know that I am a human being. I’m not a monster, despite what you may think,” he said. “There’s not a day that goes by, in the last 10 years, that I haven’t felt the deepest level of regret.”

Leah Martin, the teen’s mother, wasn’t receptive.

“I hope that every day that you sleep, you have to see her,” the teen’s mother, Leah Martin, shouted at Flowers in court Thursday. “Do you understand me? I hope you see her face and the child that you killed. You didn’t only kill my child, you killed your own.”

Court records show Martin left home one night in 2012 to speak to Flowers and never returned.

For years, her disappearance was classified as a missing persons case, and Flowers was listed as a person of interest. Eventually, it was assigned to a cold case squad that found evidence linking Flowers to her killing — even though Martin’s body had not been found.

In 2016 a grand jury indicted Flowers, who was in state custody on unrelated charges at the time, on a first-degree murder charge in the teen’s death. Six years passed before he pleaded guilty this month to a lesser charge of second-degree murder.

Flowers said Martin’s body was buried in a field in Alabama, and as part of the April 1 plea agreement, he promised to help authorities recover it in exchange for a lighter sentence.

According to court records, text messages from 2012 showed a strained relationship, with Flowers begging Martin to abort the pregnancy because having the baby could affect his existing relationship with another woman. Then 24, he was also worried about charges for having sex with a minor, officials said.

Martin decided to continue the pregnancy, choosing Ja’Leah as her baby girl’s name, the newspaper reported.

Detectives on the cold-case squad obtained cellphone tower records to track Flowers’ movements the night Martin disappeared. Records show he drove around her home and then went to his home before heading to a restaurant where he worked the closing shift.

He also visited the mother of two of his children before going back to the restaurant. He then drove throughout Tampa Bay before returning to St. Petersburg.

It was not clear why authorities believed Martin’s remains are in Alabama.

After Flowers pleaded guilty, he spoke with investigators in Alabama over a video chat and pointed them toward a specific location, Pike County Sheriff’s Office Lt. Troy Johnson told WTSP in Tampa.

Investigators there used ground-penetrating radar to search, and also brought in a backhoe to dig more than 4 feet (1.2 meters) deep during a week-long search that came up empty.

“Unfortunately, whether it was because of the many years that have gone by or because of the lack of the reliability of the information that we got, we just weren’t able to find what we are looking for,” St. Petersburg police spokeswoman Yolanda Fernandez told WTSP.