Trevor Buckley, 16, died from a gunshot wound to the chest around 1:30 p.m. at his home on the 2500 block of Paden Street in south Jackson.
Police are trying to determine if Buckley's death was a suicide or an accident, Jackson Police Department Chief Shirlene Anderson said.
Buckley's 15-year-old brother is being questioned by police, she said.
Around 10 a.m., a 55-year-old man died after being shot once in the upper abdomen, Hinds County Coroner Sharon Grisham-Stewart said.
The man, whose name is being withheld pending notification of family, was shot around 9:30 a.m at a home on the 1300 block of Eminence Row, police said.