The gunman who opened fire at former President Donald Trump at a rally was spotted by a local Swat team more than 90 minutes before the shooting, text messages reveal.
Thomas Matthew Crooks was seen sitting at a picnic table by a local Swat team sniper who alerted colleagues – a sighting much earlier than previously thought.
The messages, obtained by the New York Times and ABC News, will add to the list of security failures that preceded what authorities say was an assassination attempt.
One man was killed and three injured in the Pennsylvania attack, including the former president who was shot in the ear.
Multiple investigations have been launched into what went wrong in securing Butler Fair Show grounds on 13 July.
Secret Service Director Kimberly Cheatle resigned after admitting failures.
On the day of the shooting, the agency was in charge of security within a fenced area and local law enforcement was responsible for areas beyond that.
At 16:19 local time (21:19 BST), the local police sniper texted two colleagues who were in the second floor of a warehouse overlooking the site, telling them he was clocking off.
As he left the building, he saw a young man sitting at a picnic table and notifed the others, saying in a text “someone followed our lead and snuck in and parked by our cars just so you know”.
By 17:38 Crooks had moved from the table to the warehouse, an American Glass Research (AGR) building, and pictures of him were taken and shared in a group chat.
“Kid learning around building we are in. AGR I believe it is. I did see him with a range finder looking towards stage. FYI. If you wanna notify SS snipers to look out. I lost sight of him.”
Thirty-three minutes later, Crooks was dead, shot by the Secret Service after opening fire from the roof an adjoining warehouse.
The newly published text messages extend the time period in which the 20-year-old gunman had provoked suspicion.
Previously reports established that he was on the radar of local law enforcement about an hour before the shooting.
Witnesses told the BBC moments after the shooting that they had spotted the gunman on the roof and raised the alarm.
It is still unclear why there was a communications breakdown between local law enforcement and the Secret Service.
Members of the local Swat team told ABC News on Sunday they had no contact with the agency and a face-to-face briefing failed to happen.