CLARKSVILLE, Tenn. -- Police said someone threw a grenade through a Clarksville business window Thursday night.

Video: Hand Grenade Thrown Into Cell Phone Store

It's business as usual at the Cell Phone Doctors in Clarksville, but owner Jeff Carter and his business partner thought they were going to lose everything.

"One of the officers came up to me and said they got a bomb in there. He said a hand grenade is what it was," Carter said.

Surveillance video cameras were rolling inside, and someone outside the window can be seen throwing the grenade with enough force to shatter a glass window. The explosive bounced off the back wall and landed on the floor.

"There had been some modifications made to it enough that the bomb technician, it worried him," said Clarksville Police Department representative Tim Chandler.

Investigators identified the explosive as a live, pineapple military hand grenade.

"The Montgomery County Sheriff's Department followed with their procedure and removed it with a robot, took it to a secure area close by here and detonated it," Chandler said.

How someone got the device is the more disturbing part.

"It would be a black market. It is strictly illegal. There is no legitimate excuse to have these. The military doesn't even use them anymore," Chandler said.

Even with the businesses in close proximity to Fort Campbell, there is no indication that a member of the military is responsible, police said.

Carter was left wondering why his business was targeted.

"I couldn't imagine anyone taking it this far over a cell phone. We might have one disgruntled customer per year," he said.

The Clarksville Police Department is working with federal investigators to figure out who is responsible. The concern is that he or she could have access to more of the explosives.

The grenade was found late Thursday night while the business was closed.

Investigators said if circumstances would have been different and the grenade went off, there would have been major damage to the property and someone could have been killed.