Police were called to the Suisun Senior Center at 318 Merganser Drive around 11:25 a.m. after someone reported that a man wearing camouflage clothing and carrying a gun told seniors he was "on assignment," Cmdr. Tim Mattos said.
There were five seniors in the area of the armed man at the time, and one informed the senior center's manager, who called police, Mattos said.
By the time police arrived less than 90 seconds later, the man had left on a bicycle, Mattos said.
Two officers located Ararao behind the Sunset Shopping Center and the U.S. Post Office at 325 Merganser Drive, Mattos said.
One of the officers saw that Ararao was armed and told him several times to put the gun down, Mattos said. During the confrontation, the officer shot Ararao once in the chest.
"At some point, he became an immediate threat to the safety of the officers and the citizens around them, and the officer used force to stop it," Mattos said.
Ararao was taken to the NorthBay Medical Center in Fairfield where he was pronounced dead at 11:53 a.m., Mattos said.
Mattos said he does not know if Ararao pointed the gun at the officers.
"He did something that caused the officers to fear for their lives and those of the people in the busy area," Mattos said.
Police have had prior contact with Ararao, Mattos said.
A man who answered the phone at the senior center this afternoon said he wasn't at the center on Wednesday but was familiar with Ararao.
He said he would not consider Ararao a dangerous person.
"He would sit and have coffee and would leave in 10 minutes," said the man, who asked not to be identified.
Ararao's autopsy is scheduled for today.