"Secret Service, they are the best in the world. And they are contacted, and they train elite forces all over the world," said Cory Allen, a former Secret Service Agent who lives in the Bay Area. He served President Barack Obama after he left the White House.
The Secret Service says its agents fatally shot the suspect, who has been identified as 20-year-old Thomas Matthew Crooks, after he opened fire from a roof about 150 yards from the stage.
Allen says it is too early to point fingers at where the security lapses were. But he thinks there is a strong likelihood that there may have been a problem in the line of communication.
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"My instinct is there was potentially some kind of misunderstanding or somebody wasn't sure of what to do with the information or who was to act on it," Allen said.
Allen said the secret service costs money -- taxpayer money. And assets are assigned based on threat risk of any given event. But as he explains, sometimes the issue may be much more basic.
"Having dealt with radio failures myself. Downpours in Miami when President Obama landed in Air Force One, and my radio goes down because a thunderstorm came through. And stuff like that happens," Allen said.
"It is downright scary. It is tough to take. It is hard to think you can go somewhere and these things will happen," said Oakland resident Benjie Ross.
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He is troubled by Saturday's attack on Trump. But he is critical of the harsh criticism directed at the Secret Service. He says Americans needs to be patient until there is a full investigation.
"I think even people that are highly trained, highly skilled professionals, there may have been an oversight. Who knows? We never really know. But I think, if anything, it's going to be exacerbated in the media, then speculation, and then it kind of has a life of its own," Ross said.
"We have the Secret Service for a reason. And they can correct errors," said Professor Nolan Higdon, who teaches history and communications at Cal State East Bay.
He said there needs to be a thorough investigation into what went wrong, but cautions against politicizing the entire Secret Service.
"It tends to just end up engendering a lot of cynicism of these individuals and organizations, that despite their faults, are critical to our democracy," Higdon said. "I think it's irresponsible to blame the entire organization for whatever faults may have occurred."