No injuries were reported in either fire.
Sacramento Metro Fire Capt. Christian Pebbles confirmed to KXTV in Sacramento that Alexander Piggee, being held for a fire that devastated the Westfield Galleria at Roseville, Calif., Thursday, also was being investigated for a Walmart fire in Antelope.
There were reports that Piggee worked at the Walmart store.
Firefighters continued to put out hot spots in the Galleria Thursday night, The Sacramento Bee reported.
The full extent of the damage was not known. Officials expected to find serious water damage from the sprinkler system and firefighting efforts as well as a partially collapsed roof over two shops and smoke and fire damage.
Residents wondered when the mall will reopen and there was concern about the economic fallout from its shutdown, the newspaper said.
Piggee, 23, of Sacramento, was being held in the Placer County Jail on charges of aggravated arson and making criminal threats.
Police said he entered the mall's GameStop store, said he had a gun, ordered the workers out, locked himself inside and set the fire. The mall was evacuated.