BERKELEY, Calif. (KTVU) The vulnerability of the UPS workers going to their jobs in San Francisco Wednesday or the Congress members playing a game of baseball in Virginia has shattered a sense of peace for many Americans Wednesday.
Prayers came from both Republicans and Democrats on Capitol Hill.
California Senator Dianne Feinstein called for action.
"The continuing scourge of gun violence is incredibly disheartening. We must do more to address the causes of these tragic events," Sen. Feinstein posted on her Twitter account.
Bay Area Congressman Eric Swalwell also searched for answers.
"We want to understand what the motivation was from a law enforcement and also from a policy maker perspective," said Rep. Swalwell.
The website Gun Violence Archive, a non-profit group which tracks gun violence, shows a recent increase in mass shootings, which they define as four or more people injured or killed, not including the shooter.
The website data states there were 274 mass shootings in 2014. That increased to 334 in 2015 and 384 in 2016.
This year, the San Francisco and Virginia shootings bring the number to 154 through June 14th..
U.C. Berkeley Law Professor Franklin Zimring is director of the Criminal Justice Research Program.
He says Wednesday's shootings highlight an ongoing state of life in America where guns are readily available.
"The vulnerability that we have particularly in public spaces to being undefended against other people using lethal force," Zimring said, adding that it is difficult to explain why the numbers have increased.
Zimring does say, "The number of handguns out there has gone up in the civilian population."
He says the category of mass shootings is not recognized by law enforcement, and often it is difficult to tell in advance who will take lethal action even California's strict gun control laws offer limited protection.
"As long as ownership and availability are very high, the capacity of those laws to stand between handguns and people that want to acquire them is quite limited," Zimring said.
One study in 2016 by Harvard and Northeastern Universities estimates 55 million Americans are gun owners, with a slight decrease in gun ownership from 25% of the U.S. population in 1994 to 22% in 2015.