A federal grand jury has indicted a Honolulu man for what officials say were planned bomb or chemical weapons attacks on Oahu, including a high-rise apartment building.

Ethan Sandomire, 20, has been charged with possessing and attempting to possess a chemical weapon, and possessing an unregistered destructive device. Sandomire was taken into custody in late March at his Waialae Iki home on allegations he was making a pipe bomb, according to federal court records and news reports. He has been in custody since then, a spokeswoman for the U.S. Attorney’s office said Thursday.

The U.S. Attorney’s Office says the charges stem from actions Sandomire took between December and March, including researching explosive and chemical weapons and writing privately about his plans for attacks. He used the name “Pyro Pelican” on social media, the indictment says.

Officials say he ordered the materials to make a destructive device online and they were delivered to his residence.

The FBI seized the items including approximately 30 pounds of aluminum powder, approximately 30 pounds of ultra-pure potassium perchlorate, approximately 45 pounds of potassium perchlorate, and multiple ignition systems, wireless firing systems, and victim-initiated tripwire systems, according to a press release.

Sandomire apparently planned to blow up or release chlorine gas, which he’d acquired the elements needed to produce, at a 40-story, 450-unit residential apartment building in central Honolulu. The building, which was not identified, includes a multi-level grocery store on the lower level, according to the indictment.

In February, he visited the apartment complex, took pictures of structural support columns and even asked the front desk staff for copies of the building’s floor plans, the indictment said.

“Sandomire’s personal computer contained a desktop note entitled ‘destroy (Building A)’ by using chemicals and explosives, among other things, and numerous folders with extensive research into explosives, chemical weapons, biological weapons, improvised munitions, and similar topics,” the press release said. “The folders contained digital versions of approximately 54 books about explosives and related topics. Sandomire’s computer also contained an instructional document titled ‘Advanced Chemical Weapons Design and Manufacture,’ with the subtitle ‘Chemicals that Kill in 30 Seconds or your Money Back.'”

Sandomire is facing charges that carry penalties of, among other things, life imprisonment and a fine up to $250,000.

The press release did not say how federal officials learned about Sandomire’s alleged plans.