Grossl, 54, said he had calmed down some today but was still angry.
''I didn't know if these guys were armed or not,'' Grossl said.
Grossl, armed with a .410-gauge shotgun, held the two 16-year-old boys from South Bend on the floor of his Hesston-area home in LaPorte County until police arrived.
He said he shot one of the boys when he failed to keep still while on the floor.
Grossl said he was inside his pole barn about 2:30 p.m. Tuesday when his beagle started behaving strangely at his property in the 7800 block of North Fail Road. He put the dog on a leash outside then noticed the back sliding glass door on his house was open.
''I knew something was bad wrong,'' said Grossl, explaining how he then went inside and noticed several of his firearms leaning against a kitchen chair.
Grossl grabbed the shotgun and made sure it was loaded, then ventured into a small bedroom where he found one of the boys.
He forced the boy onto the living-room floor then heard a crash. Something had been thrown through the window of another bedroom, where Grossl found the second boy.
According to police, a third person was in the home but fled in a vehicle. That person, also believed to be from South Bend, remained at large today, according to LaPorte County Sheriff Mike Mollenhauer.
The sheriff said officers today were checking areas where they believe he might have fled.
Grossl said he was holding the boys next to each other on the floor but one of the boys kept sitting up and moving around. Finding his 9 mm gun missing from a bookcase, Grossl said, he didn't know if it was in the hands of one of the boys, and he shot the one teen who wasn't fully complying with his orders to remain still.
''They kept wanting to talk to each other so I shot him to the floor. I was scared for my life,'' Grossl said.
Police described his wound as superficial.
Both juveniles were being held in the LaPorte County Juvenile Services Center, suspected of Class B felony burglary.
The LaPorte County prosecutor's office said charges against Grossl are unlikely because his actions were from a desire to preserve his own safety.
Grossl said it's a wonder he didn't shoot both of the boys given the intensity of the situation he found himself in.
''I shook for four or five hours after this happened,'' Grossl said.