PULASKI, Tenn. -- Police in Giles County have arrested an 18-year-old man for allegedly setting a fire that killed a mother and her two children on Friday morning.

Related: Images | 6 p.m. Report | 5 p.m. Report | Noon Report | RAW VIDEO: Police Investigate Fire

William Charles Angel Jr. has been charged with three counts of first-degree murder.

Giles County fire chief Barry Witt said the blaze occurred on Milky Way Drive near Pulaski, Tenn., at about 1 a.m.

Crews said there was not much they could do when they arrived because the house was fully involved. A propane tank near the home made the fire more intense.

Crews later found three bodies inside the home. The victims were identified as Desere Thornton, 38, Jerrod Thornton, 16, and 9-year-old Anthony Thornton.

Police said earlier in the day they questioning several people of interest in the case.

Originally, there was speculation that some juveniles may be responsible, based on some witness statements. However, the sheriff said all of the people being questioned are adults.

Giles County Chief Deputy Tommy Chapman said the state fire marshal was assisting in the investigation and the Tennessee Bureau of Investigation was notified.

Angel's motive for setting the fire was unclear. Police said they are still investigating and more arrests could be made.

The Thorntons had lived in the home for about six weeks, but residents said their family had lived in Pulaski for years.

"They're just good people. Everyone liked them. She was the sweetest girl," said Robert Rochester, a friend of the family.

Thornton owned a local gym, where a wreath was hung Friday afternoon in her memory.