SAN FRANCISCO (CBS SF/AP) — Jason Cortez, a beloved San Francisco firefighter-paramedic who was killed during a training accident last week, was knocked over a third-floor railing by a water blast from a valve he had “inadvertently” opened, authorities said in a preliminary report released Sunday.

READ THE REPORT: Preliminary Summary Report of SFFD Line of Duty Death

SFFD firefighter paramedic Jason Cortez (SF Fire Dept.)

Cortez, 42, was participating in a training drill Wednesday when he was injured. The married father of two died an hour later at a hospital. Fire officials previously described his death publicly as a “training accident.”

His death has rocked the department.

“Jason worked in a variety of assignments and was loved and respected by his colleagues,” the fire department said in a statement. “We are aware of the many speculative reports citing what may have occurred, and ask that you respect Jason, his family, and our department as we determine the factual causes that lead to this tragedy … Our hearts go out to his family and loved ones, especially his wife and two young children.”

The tragedy may have been compounded by confusion about protocols designed to limit the spread of the coronavirus, according to a copy of the five-page report released on Sunday.

Only four firefighters — half the typical amount — participated in Wednesday’s “pump drill” exercise meant to train a rookie.

SFFD Firefighter Death Investigation

Third floor fire escape and standpipe outlet. (San Francisco Fire Dept)

For reasons that aren’t known, Cortez left other firefighters who were dousing a simulated fire on the third floor of a training tower and went to a fire escape, the report stated. There, he “inadvertently” opened a valve — possibly intending to drain water — that did not have a hose connected to it, and a stream flowed out at as much as 100 pounds per square inch pressure.

“The stream of water coming from the (valve) struck him in the chest, knocking him backwards into the fire escape railing, causing him to fall backwards off the fire escape,” according to the report.

Cortez, the son of a retired San Francisco firefighter, was assigned to Station 3 in the Tenderloin, one of the busiest in the city.

A 13-year veteran of the department, he worked his way up the ranks of the department starting as an ambulance paramedic at Station 49, then going to the SFFD Academy and graduating as a paramedic and firefighter.

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