In the hours after an explosion damaged a suburban Tampa Bay area house, police made a disturbing discovery in the home of one 85-year-old neighbor.

Hand grenades. Machine guns. A ski mask. Police badges. Numerous books on munitions, weapons and "detonating devices," including one tome titled "How to Kill-Vol. 1."

The neighbor, William Metz, was arrested and charged with several weapons counts. Tarpon Springs Police say Metz is a felon who wasn't supposed to have the small arsenal in his home.

"He's very dangerous," Tarpon Springs police Chief Robert Kochen said. "Most of your neighbors don't have stuff like this."

During a Tuesday afternoon news conference, Kochen said Metz "didn't stand out" until the Monday incident.

Authorities say residents of Metz' quiet suburban neighborhood reported a loud bang at a home early Monday morning. The Tampa regional bomb squad was called in to investigate and found a hand grenade had detonated in the home's backyard. The blast damaged the home, shattering rear windows and breaking concrete. Police say four people inside the home were not hurt.

Police executed a search warrant on Metz' home and found military-grade explosives, including anti-personnel mines, a shotgun and a hand grenade.

The investigation continues, and officials say Metz has not been charged in connection with the explosion.

Metz doesn't have a criminal record in Florida. But in 1947, court records from New York show, Metz was convicted of robbery and later violated his parole in the 1950s, when he was accused of escape, felonious assault and carrying a dangerous weapon.

Metz is being held on $150,000 bail at the Pinellas County Jail.