It sounds like both men entered the bar together:

Helus and the unnamed CHP officer were the first law enforcement officers to respond to the shooting.

“When Ventura County Sheriff’s Sgt. Ron Helus and a CHP officer entered the bar, the suspect attacked almost immediately, firing multiple rounds at both men,” Ayub said. “Sgt. Helus was struck five times by gunfire from the suspect. Both men quickly retreated and fired their rifles at the suspect.”

It was at that point that the CHP officer accidentally shot Helus once.