“When our deputies went through the door initially he was still firing rounds,” Santa Clara County Sheriff Laurie Smith told journalists.
The gunman opened fire early at around 06:45 local time (14:45 GMT) on Wednesday in the VTA light rail yard and according to reports, the attack unfolded during an employee meeting.
Law enforcement officials identified the gunman as 57-year-old Samuel Cassidy and his ex-wife Cecilia Nelms revealed that Cassidy had told her that he wanted to kill his colleagues, but she had never believed he would do it.
Deputy Russell Davis, a spokesman for the Santa Clara County Sheriff’s Department, said “deputies did not exchange gunfire” with the suspect.
“Preliminarily, we’re going to go with the assumption it was a self-inflicted gunshot.”
Just before the shooting, a fire broke out at a home belonging to Cassidy, according to local media.
The Santa Clara Valley Transport Authority operates three train lines making up over 40 miles (65km) of rail. It also operates about 70 bus lines in the city.
Speaking from near the crime scene, Governor Gavin Newsom condemned the “rinse and repeat” cycle of US mass shootings.
In the same vein, US President Joe Biden called the attack a “horrific tragedy” and ordered flags to be flown at half-mast as he again urged Congress to take action on gun control.
“Every life that is taken by a bullet pierces the soul of our nation, we can and we must do more.” Biden said