After more than a year and thousands of hours of investigation, three men have been charged with murder and other crimes in a July 2015 quadruple homicide at a home in rural South Carolina, a sheriff said Thursday.

Orangeburg County Sheriff Leroy Ravenell said 17-year-old Shamekia Sanders, 14-year-old Tamara Perry and 28-year-old Krystal Hutto all died of bullet wounds to the head July 15, 2015, at a home outside of Holly Hill. Fifty-year-old Jerome Butler also was killed, while an 8-year-old boy was critically injured.

"I made the comment the day this happened during the news conference at the scene that we would not rest until the person or persons who committed this crime are brought to justice," Ravenell said.

Ravenell told reporters that the three men arrested lived in Eutawville about 10 miles from Holly Hill and about 60 miles northwest of Charleston.

He said 27-year-old Derrick Warren Coleman and 35-year-old Anthony Jermaine Scott were arrested this week in Baldwin County, Alabama, where Coleman is originally from. They are expected to be returned to South Carolina in the next few days, the sheriff said.

The third man arrested, 37-year-old Robert Lee Bailey, appeared at a bond hearing in Orangeburg later Thursday. Shackled and dressed in an orange jail jumpsuit, he protested his innocence to a magistrate.

"I'm not no murderer. There's no way I would ever hurt anybody," he said.

Each defendant faces four counts of murder, one count of attempted murder, a count of burglary and a count of possession of a fire arm during the commission of a crime.

The magistrate said a circuit judge would have to set bond on a murder charge and gave Bailey a form to fill out if he wants a public defender. About two dozen relatives and friends of the victims were in the courtroom but they didn't want to comment.

Online jail records did not indicate if the two men arrested in Alabama have attorneys.

Ravenell has said drugs were being sold from the house where the four were killed. He said burglary was the motive but also said drugs were involved. He did not provide details about why the arrests came when they did. And the sheriff added that the case is still under investigation.

He said there could be more charges against people who knew about the robbery before it happened or the slayings after they happened.

Following the slayings, a task force of state, local and federal officials was formed to investigate the case.