A Pennsylvania man who was arrested on weapons charges at a “No Kings" protest against the Trump administration on Saturday is facing more than two dozen additional charges after investigators said they found a cache of homemade bombs at his home outside Philadelphia.

The man, Kevin Krebs, 31, of Malvern, Pa., first caused alarm among people in the crowd at the protest in West Chester, Pa., when he tried to hide a Sig Sauer P320 handgun under his raincoat and another layer of clothing, the authorities said.

The protesters pointed him out to law enforcement officers, who said that they found nine fully loaded magazines, a bayonet, pepper spray and a ski mask on him and an AR-15-style rifle on the back seat of his Ford Explorer. Mr. Krebs did not have a license for the handgun he had on him, the police said.

During a search of Mr. Krebs’s home on Monday, the police discovered 13 improvised explosive devices, in addition to military-style body armor vests and several drawings of grenades, the authorities said on Tuesday.

According to a probable cause affidavit, the cache included pipe bombs and explosives that were made from a glass Coke bottle and a can the size of an energy drink. Some were filled with nails, screws and pellets.

All of them were disposed of by the bomb squad from neighboring Montgomery County, said prosecutors, who noted that night vision goggles and a gas mask had also been recovered from Mr. Krebs’s vehicle on Monday night.