CHESAPEAKE, Va. (WAVY) — Sheriff Jim O’Sullivan knows what it takes to prepare for a presidential campaign rally in a highly-charged political environment.

Two weeks before former President Donald Trump survived an assassination attempt in southwestern Pennsylvania over the weekend, O’Sullivan was making sure that didn’t happen on his watch.

Trump held a rally June 28 in an open field at historic Greenbrier Farms in a rural section of Chesapeake, a setting similar to the Farm Show and Fairgrounds in Butler, Pa.

Thomas Matthew Crooks, 20, of Pittsburgh suburb Bethel Park about an hour away from the Trump rally site in Butler, was able to scale a building less than 150 yards away from where Trump was speaking. He had a clear line-of-sight to the former president and fired several shots. He wounded Trump in his right ear, but killed another man and wounded two others.

O’Sullivan recalled his first order of business once he knew Trump would be on his turf, which turned out to be a short five days before the former president touched down.

“On Sunday when we got notified, the number one thing that we looked at is line-of-sight and high-ground command,” O’Sullivan said in a Monday interview. “If there is high ground and line-of-sight, you have to block it with some kind of structure.”

O’Sullivan said he made sure no such opportunity existed for a would-be assassin.

“If there was anything deemed as high ground or line-of-sight, it was taken care of,” O’Sullivan said. “There was no longer high ground with line-of-sight. And I’m talking line-of-sight as far as the eye can see, not just 150 yards, [but] a lot longer than that, over a thousand yards.”

O’Sullivan said depriving anyone with bad intentions and a rifle the high ground and line of sight is “basic law enforcement.”

NBC News quoted a Secret Service spokesman in saying that some of the counter-sniper teams at the Butler rally Saturday were actually from local Butler County tactical units, and not from the Secret Service.

O’Sullivan wouldn’t comment whether any local snipers were used in Chesapeake.

He said he would have felt “awful” if the assassination attempt had happened two weeks earlier, but was proud of the security provided by a coordinated group of agencies for the Chesapeake rally.

O’Sullivan acknowledged the participation and contribution of partner agencies to help keep the Chesapeake Trump rally safe.