The blast happened after 7 p.m. Monday at a home in Lowell near 181st Avenue and Interstate 65. The home was leveled, and a neighboring home caught fire.
"It just sounded like a really big thunderstorm and lightning struck right next to your house," neighbor said Jonathan Kendall.
Authorities say Victor Strain was a neighbor who was housesitting. He reportedly went to check on the house at 108 East State Road 2 because he smelled something.
"He went to check on the house. He thought he smelled smoke; something was burning in the backyard, back area of them home. There was an explosion. He was killed instantly," said John Buncich, sheriff, Lake County, Ind.
Strain, who was in the basement of the home, was pronounced dead at the scene shortly after 12 a.m. Tuesday.
Home video during the blaze showed the intense fireball that incinerated most of what was in its path.
Debris from the explosion flew as far away as 100 yards in every direction. Wood, glass, nails, and a mattress could be seen stuck in a nearby tree Tuesday.
Chopper7 HD was live over the scene as more than 100 firefighters and police responded and worked overnight.
The cause of the explosion was a leak from a tank capable of holding 500 pounds of propane.
Wayne Wietbrock, a friend of the absent homeowner, came by the see the damage Tuesday.
"He's been in a nursing home with Alziemer's for the last few -- quite a few months. People just check on the house to make sure it's alright. Nobody has lived in the house since last winter," Wietbrock said.
Firefighters say the destruction and the propane leak are reminders for anyone leaving a home unattended for a long period of time.
"If they had the propane still on even though there was nobody living there, a leak could have developed from anywhere, any of the appliances supplied by propane in the house, and [gone] undetected until which time the neighbor went to check on the house," said Clint Gorball, Lowell Fire Department.
The home next door was also damaged by the fire and the explosion, but no other area residents were hurt.
A firefighter, however, did suffer a minor knee injury while battling the blaze.