Local, state and federal authorities continue to investigate suspected explosive materials in the wake of a Wednesday morning shooting by a South Bay transit employee who killed eight people and himself at a light rail yard in San Jose.

Jimmy Etan, an IT employee at Santa Clara Valley Transportation Authority, describes the mass shooting incident that occurred o the morning of Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

Investigators, law enforcement officials and political leaders held a briefing Wednesday afternoon to shed more light on the shooting by a Santa Clara Valley Transportation Authority employee identified by various media outlets as Samuel Cassidy, 57.

A spokesman for the Santa Clara County Sheriff’s Office said that explosive-detecting dogs and robots and members of the sheriff’s bomb squad are expected to remain at the VTA’s Guadalupe rail yard on West Younger Avenue into Thursday to ensure it is safe.

Deputy Russell Davis, Public Information Officer for the Santa Clara County Sheriff’s Office, speaks at the press conference about the mass shooting at Valley Transportation Authority Guadalupe facility in San Jose, Calif., on Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

“We’re going to be there throughout the night to clear every room and every crevice of that building,” Deputy Russell Davis said.

Investigators with the FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are also supporting the Sheriff’s Office in investigating the shooting and supplying investigators with assets like ballistics and forensic equipment from the FBI’s offices in Quantico, Virginia.

Special agent in charge of the San Francisco Division of the FBI, Craig Fair, announces that the FBI would be assisting the Santa Clara County Sheriff’s Department with the investigation of the mass shooting in San Jose, Calif., on Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

The sheriff’s office first received reports of the shooting at 6:34 a.m. and dispatched deputies to the rail yard, which is adjacent to the Sheriff’s Office’s headquarters.

The gunman opened fire during a shift change at the rail yard, with graveyard shift employees leaving the facility and day shift employees arriving, according to Davis.

More than 40 employees were at the facility at the time, San Jose Police Chief Anthony Mata said. One shooting victim is still in critical condition at a local hospital in addition to the eight victims confirmed dead.

In addition to the FBI and ATF, local law enforcement in Santa Clara County, the California Highway Patrol, the state’s Office of Emergency Services and the U.S. Department of Homeland Security assisted during the initial active shooter response.

Active shooter team of the Santa Clara County Sheriff’s Office boarding a van on West Younger Avenue in San Jose, Calif., on Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

Davis and Santa Clara County Sheriff Laurie Smith argued that the death toll could have been even higher if law enforcement officers hadn’t responded as quickly as they did.

“The deputy sheriffs from the sheriff’s office, the officers from San Jose Police Department ran into the building while shots were being fired and I know that it saved many lives,” Smith said at the briefing.

Davis noted that sheriff’s deputies did not exchange gunfire with Cassidy and investigators are working under the assumption that he died by suicide.

Davis did not confirm whether a house fire at what is believed to have been Cassidy’s home was connected to the shooting.

Local officials at the briefing expressed grief and outrage about the shooting, which came less than two years after Gilroy resident Santino William Legan, 19, shot and killed three people and injured 15 others at the Gilroy Garlic Festival in July 2019.

Governor Newsom speaks to the media regarding the mass shooting at Valley Transportation Authority Guadalupe facility in San Jose, Calif., on Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

“To the victims, to those who’ve lost their lives and the families lost their loved ones, our hearts go out, but we are resolved to not make this meaningless, but to bring meaning at this tragic moment in our state and our nation’s history,” Gov. Gavin Newsom said.

County Supervisor Cindy Chavez noted that VTA continued service amid the shooting and only stopped when the transit agency issued an indefinite pause of light rail service at noon.

“These heroes — we all learned how to call essential workers ‘heroes’ — we’re now calling on them to be heroes again,” she said.

The city of San Jose will hold a vigil for the victims of the shooting Thursday at 6 p.m. at San Jose City Hall, located at 200 E. Santa Clara St.

The Santa Clara County Sheriff’s Department announced that nine people, including the suspect, were dead in the shooting at Valley Transportation Authority Guadalupe facility in San Jose, Calif., on Wednesday, May 26, 2021. (Harika Maddala/Bay City News)

The San Jose-based community organization Working Partnerships USA and the South Bay Labor Council set up a fund to support families of the shooting victims. Donations can be made at bit.ly/vtasolidarity.

A family reunification center has also been set up at the County Government Center at 70 W. Hedding St. VTA employees and their families can call (408) 321-7550 for more information.

“We know that our entire community will need this moment and many others to mourn together,” San Jose Mayor Sam Liccardo said. “So we want to bring people together to be able to at least share a common humanity, particularly given all that we’ve been through over the last year-and-a-half, this is a time when we need to be together.”