The single-engine plane crashed into the Harbour Trees Golf Club, which winds through a neighborhood along Morse Reservoir in Noblesville, early Thursday evening. The plane smashed to a halt in a sand trap next to a putting green, leaving scorch marks on the nearby fairway.
The names of those killed weren't immediately released.
Federal aviation investigators would return to the golf course Friday to try to determine the cause of the crash, Noblesville police Lt. Bruce Barnes said.
Nearby resident Eric Smith told The Indianapolis Star that he was the first person to reach the plane after it circled above the golf course near his home and then "corkscrewed" into the ground.
He said the crash sounded "like a gunshot - one thump, then done."
Smith said he pulled away a wing that was lying on top of one of the occupants, but that the man had no pulse. Only when emergency personnel arrived did he realize there was a second man in the plane.
Another witness said nothing appeared wrong until just before the crash.
"All of a sudden the left wing just dropped," John Clayton told WRTV. "I never did see it come up from the tree line."