A Honolulu resident, who was charged Wednesday for possessing a chemical weapon and an “unregistered destructive device,” allegedly planned an explosive and chemical attack on a large apartment building on Oahu, federal authorities say.

Ethan Sandomire, 20, was arrested by FBI agents on March 29 and was indicted by a federal grand jury Wednesday for alleged offenses between December and late March

According to the federal indictment, he allegedly bought the ingredients to create chemical and explosive weapons with plans to destroy a large, “centrally located” apartment building in Honolulu.

He is being held without bail in the Federal Detention Center.

Sandomire is accused of ordering a list of items, including dozens of pounds of chemicals used in explosives, ignition systems, wireless firing systems and trip-wire systems, according to the U.S. Attorney’s office.

He also allegedly bought items from an Oahu hardware store in February that, when combined, can create chlorine gas, which can be fatal when inhaled, the indictment said.

Sandomire allegedly searched for blueprints and floor plans for an unidentified apartment building in Honolulu that contains about 450 residential units, commercial units and a multi-level grocery store.

On Feb. 26, according to the indictment security footage shows Sandomire entering the 40-story building.

The indictment accused Sandomire of taking photos of the building, including of structural support columns inside the parking garage, a large storage area and air vents that serve a 16,000-foot space in the building.

He allegedly asked the front desk staff for the building’s floor plans, which they did not provide, but the court documents say he found the apartment building’s floor plans online, and searched for the number of people living in the building.

Sandomire’s computer was found to have a note with a list of vague instructions to destroy the apartment building, fill a populated area with “nerve gas,” “spawn bio weapons” in the food and water supply, start fires in the building, and collapse it.

His computer was also found to have several folders illustrating his alleged research into explosives, chemical weapons and improvised munitions, federal officials said.

Some of the folders were titled “building demolition,” “My Attack Plan,” and “bio warfare,” according to court documents.

His computer included a document showing how much explosives would be needed to destroy a concrete pillar.

He also allegedly did online research of people involved in mass killings.

Sandomire was hospitalized in August and September last year after suffering a burn when he threw explosive powder onto a heat source, the indictment says.

“Even though Sandomire went to great lengths to obtain the knowledge and the materials to construct a chemical weapon and an explosive device, the men and women of the Honolulu FBI disrupted his evil intentions before he could cause harm. Wednesday’s indictment is an example of the FBI’s commitment of making Hawaii a safer place for all,” FBI Special Agent in Charge Eli Miranda said in a statement.

Sandomire’s charges include one count of possession of a chemical weapon, the maximum sentence of which is life imprisonment, and a fine of up to $250,000, and possession of an unregistered device, which has a maximum sentence of 10 years in prison and a fine of up to $10,000.