Marine Cpl. Jonathan D. Porto and his wife, Rachel, were expecting a baby when he was deployed to Afghanistan in December.
Ariana Ralyn Porto was born two months ago, but Porto, 26, of St. Petersburg never got to meet her.
He was killed in an accident Sunday in Helmand province, Defense Department officials said.
They declined to provide details on the accident, citing privacy rules, but his uncle said family members were told that he died when his vehicle flipped and he was pinned in the wreckage.
His body arrived Tuesday at Dover Air Force Base in Delaware.
"It's a tragedy all the way around," said his uncle, Craig Gregoire.
Porto joined the Marines in March 2008 and was promoted to corporal Dec. 1, said Lt. Timothy Irish. He had received several awards for his service.
He was deployed to Afghanistan, where he served as a small-arms repair technician for the 1st Battalion, 6th Marine Regiment, Regimental Combat Team 7, Marine Expeditionary Brigade-Afghanistan.
Porto is survived by his wife, who is 23, and their 2-month-old daughter. He was stationed at Camp Lejeune in North Carolina. His mother, Rachel Bernaby, and stepfather, Brian, were not at their St. Petersburg home on 46th Avenue N Tuesday afternoon.
An American flag and a red Marine Corps flag were at half-staff outside their front door.
Porto was born in St. Petersburg and has seven brothers and sisters, said Gregoire.
Porto graduated from Timberlane Regional High School in Plaistow, N.H., in 2002, according to associate principal John Leary. He remembered Porto as a hands-on learner who was a good kid.
Finding out Porto ended up with the Marine Corps "did not surprise me," he said.
Gregoire of Hendersonville, N.C., said he thought his nephew "found a sense of purpose" in the Marine Corps.
"Whenever I saw him at a family gathering, he gave hugs freely, smiled widely and often, and pretty much made me feel cheerful and welcomed," said Porto's aunt, Renae Gregoire.
Staff writers Kim Wilmath and Kameel Stanley and researcher Carolyn Edds contributed to this report.