Sheriff: Device found at Trident Tech contained ammonium nitrate, nails

Published: Dec. 21, 2012 at 3:29 PM EST|Updated: Dec. 21, 2012 at 8:52 PM EST
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William McGrath (Source: CCDC)
William McGrath (Source: CCDC)

NORTH CHARLESTON, SC (WCSC) - Sheriff Al Cannon said Friday a man was arrested after leaving a homemade explosive device in a parking lot near a Trident Technical College building earlier this week.

The device, which was rendered safe by a bomb squad Monday, contained ammonium nitrate and featured an igniting source with nails taped to it, Cannon said.

Ammonium nitrate is commonly used in agriculture as a high-nitrogen fertilizer, and it has also been used as an oxidizing agent in explosives, including improvised explosive devices.

Trident Tech's Rivers Avenue campus was evacuated around 5 p.m. Monday after officers were tipped off to a credible bomb threat, Cannon said. Law enforcement was on scene for several hours investigating after the item was discovered in the bushes at the parking lot.

Charleston County deputies took 35-year-old William Gregory McGrath into custody this week after searching his apartment, Cannon said. McGrath's apartment was located at 2605 Elms Plantation Blvd, Apt. 634.

According to an affidavit, investigators found commercial fireworks and trace amounts of ammonium nitrate in McGrath's storage shed.

McGrath has been charged with possession or threat to use a destructive device. Additionally, McGrath was charged with the growing of marijuana after a search of his residence uncovered eight marijuana plants.

McGrath was granted a $125,000 bond Friday.  During the hearing he admitted to having the marijuana.

Cannon said investigators do not believe anyone else was involved, nor do they think McGrath had any recent connection with the school.

The college is closed right now for winter holiday, so there were very few students on campus.

The Federal Bureau of Investigations, Bureau of Alcohol Tobacco Firearms and Explosives, Homeland Security Investigations, North Charleston Police Department, and Trident Technical College assisted in the joint investigations and are expected to have representatives at the press conference.

ATF officials said the investigation was ongoing.

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