I am not a law enforcement or security expert but, as a White House advance aide, I did train with and work closely with the Secret Service in protecting President Jimmy Carter. I was shocked to see the near-fatal mistakes this elite federal protection service made at former President Donald Trump’s campaign rally.

Before I started advance assignments, I was briefed by Secret Service agents on the roles they play in safeguarding the president along with tactics they employ, from risk assessment to handling an attack or medical emergency. Agents took us through table top drills so advance staff knew how every threat or actual occurrence would be handled; nothing was left for chance.

I remember at one outdoor rally site, we led threat assessment agents through the entire route the president would take to reach the stage. At one point, the lead site agent walked on the outdoor stage and stood at the podium, scanning the nearby area and said he wanted local police to guard every rooftop that had a site line to the stage to prevent an assassin from using that location to fire at the president. He also ordered local officers to prevent employees from entering nearly office buildings with windows facing the stage for a similar reason. Several hours before the president took the stage this agent made sure that all bases were covered in the security perimeter including rooftop guards.

Based on my experience, I cannot understand why a shooter was allowed to climb a rooftop and fire at Trump. This total lapse in security nearly cost the former president his life. Other missteps that I identified include agents allowing Trump, while he was being taken from the stage, to pause and fist pump the crowed, which exposed his head and upper torso to a potential bullet. Agents allowed him to do the same as he entered his SUV again which exposed him to further harm.

Agents taught me to always assume that there is more than one attacker even though the primary has been taken out. Agents who allowed Trump to pause his evacuation and fist pump the crowd were derelict in their sacred duty to protect the former president at all cost. When Ronald Reagan was shot as he exited the Washington Hilton Hotel, video footage shows agents pushing the president head first into the limo and immediately rushing the president out of harm’s way. In Trump’s case, once he was placed in his vehicle, it did not move from its stationary site for minutes rather than quickly moving from the threat scene to the hospital.

An independent commission of high level and experienced law enforcement and military tactical leaders must quickly investigate the security failures we witnessed and identify best practices for the Secret Service to employ.

Billerica resident Rick Pozniak, who also advanced trips for First Lady Barbara Bush, has spent decades in public affairs and crisis communications which he now teaches at local colleges.