The 19-year-old man accused of killing beloved Belle Glade grocery store owner and bass fishing champion Jimmy McMillan admitted his guilt Saturday after authorities sewed together surveillance footage and tips from area residents, the Palm Beach County Sheriff’s Office said Sunday.

Corey Graham Jr. told his father that he was responsible for the “robbing, shooting and killing” of McMillan, 49, in the early hours of Jan. 2, according to a probable-cause affidavit released by the sheriff’s office Sunday afternoon.

“We’re just so glad that the sheriff’s department didn’t let this go,” McMillan’s mother, Linda, said after a news conference Sunday. “We know from the outpouring of the community he made an impact on a large amount of people.”

Graham was charged late Saturday with first-degree murder with a firearm, aggravated assault with a firearm and armed robbery with a firearm. If convicted, he could receive the death penalty.

Graham had no prior arrest record. He is a first-year student at Palm Beach State College and, before that, attended Glades Central High School, where he played offensive lineman on the football team and made The Palm Beach Post’s All-Area first team for the 2010 season.

Graham’s father, Corey Sr., had tears in his eyes Sunday morning after Palm Beach County Court Judge Nelson E. Bailey decided during the young man’s first appearance in court that he would be held without bond.

According to the probable-cause affidavit:

An anonymous source, who called Graham by his nickname “CC,” told detectives Graham had driven to McMillan’s store, waited a few minutes and then went inside to rob the shop. The source said Graham fled the store and described the black .38-caliber revolver used in the shooting.

Graham initially denied he had anything to do with the crimes. He came to the sheriff’s office voluntarily Friday with his mother, and willingly provided a DNA sample.

Meanwhile, detectives saw in store surveillance footage that the shooter had demanded that McMillan empty a cash drawer into a plastic bag. When McMillan obliged, he reached toward the shooter’s right hand, which held a gun. The shooter jumped back and fired at McMillan’s shoulder.

That hand had markings on it, and detectives concluded that a tattoo reading “Errica,” the first name of Graham’s mother, matched the markings seen in the video.

After authorities gained a search warrant to photograph Graham’s body Saturday, he was taken to the sheriff’s office. That was when he admitted his guilt to his father, the affidavit said.

“Why did you do it?” his father asked.

For the money, Graham said.

“Why did you shoot the man?” his father continued.

Because McMillan reached for the gun, Graham said.

Graham comes from a strong family, said Randy Williams, a former Glades Central assistant coach.

In his high school classes and on the practice field, he did “enough to get by,” Williams said.

“As a teammate, he was a jokester. All the kids joked around with him. Nobody had problems with him.”

Graham did not appear to be interested in playing football after high school, though.

McMillan’s mother grieved at her family’s loss this morning.

“We lost not only our son,” Linda McMillan said after the news conference. “My daughter-in-law lost her husband. She doesn’t want know what she is going to do.”

McMillan was the family’s breadwinner, and was held in high esteem by both his family and the community.

Residents have said McMillan often gave credit to residents who lacked cash, cooked meals for the unemployed and hired area residents.

His great-grandfather opened the Alabama Georgia Grocery in the 1940s, and Linda McMillan and her husband eventually bought it after she had worked there as a teenager.

The day after his death, many friends of the McMillan family and store customers filled out a poster that covered the shuttered metal doors of the store.

“We will miss you,” wrote Sarah Pittman. “Your jokes, your laugh and sneaking up behind people scaring the heck out of them. You were a good boss when I worked here. Rest in Peace, Jimmy.”

Palm Beach Post staff writers John Lantigua, Bill DiPaolo and Sonja Isger contributed to this report.