Capt. Rob Mendel, a 23-year veteran of the King County Sheriff's Office, watched in horror from the grandstands as the pilot of a highly modified P-51 Mustang lost control of his aircraft, which shot skyward before plunging into spectators on Friday at the National Championship Air Races in Reno, Nev.

Mendel — who has been flying single-engine planes since he was a teenager and has attended the annual air-race competition more years than he can remember — raced to the top of the grandstand to get a better view of the chaotic scene unfolding on the airfield below.

Behind him, he spotted a mobile command center, a 38-foot-long RV belonging to the Reno-Tahoe International Airport Authority which was being manned by Fire Chief Pete Dolan.

Air-show announcers asked for volunteers with medical expertise to come forward to help the injured and told other spectators to leave the area.

After calling his wife — a sergeant with the Sheriff's Office — to let her know he was OK, Mendel, who was on vacation with a friend, approached Dolan to offer his help. For the next four hours, Mendel and his friend stuck close to Dolan, helping the fire chief as he took command of the massive emergency response.

As of Wednesday, 11 people had died as a result of injuries suffered when the World War II-era airplane crashed to the tarmac, including pilot Jimmy Leeward and four people with ties to Washington state. More than 70 people were treated for injuries, some of them life-threatening, in the unexplained crash that sprayed shrapnel and debris at fans.

"I could tell it was going to be a very difficult scene for the local authorities to manage," Mendel said at a news briefing Wednesday in Sheriff Sue Rahr's office.

Mendel, who commands the Sheriff's Special Operations Division, overseeing the SWAT team, bomb squad and hazardous-materials team, has received advanced Incidence Response Training, which was mandated by the federal government a decade ago after the 9/11 terror attacks.

The point of that training was to ensure that police and fire officials could step in and lend their expertise during any incident in any city in the country, said sheriff's spokesman Sgt. John Urquhart.

"They get integrated in because they know how to operate in that environment," he said, noting that as a cop or firefighter moves up the ranks, his or her training becomes more specialized.

As a captain, Mendel had been trained in unified command, where one person takes control of an incident and assigns tasks to the police and fire units responding to an emergency.

"I knew all the police officers would be tied up trying to secure the scene," while firefighters were busy attending to the injured, Mendel said.

"I knew the command post needed to get there to make some semblance out of the scene."

While his friend took notes and documented Dolan's orders, Mendel helped Dolan maneuver the RV onto the runway and helped deliver the chief's assignments.

"I was just kind of the administrative aide," Mendel said of his role.

He commended the local agencies, who came together seamlessly to respond to one of the worst air-show disasters in recent history. He said spectators who could help stayed, while those who couldn't got out of the way.

"I saw a distinct parting of the people ... and then an inflow of individuals who could help," he said.

Despite the horror, the scene was remarkably calm, Mendel said.

"It's kind of like panic starts with one person, so if a number of people are being calm, it kind of calms the whole crowd," he said. "Everyone did an awesome job in the midst of just a horrific situation."

Information from The Associated Press is included in this report.

Sara Jean Green: 206-515-5654 or sgreen@seattletimes.com