Trump shooter Thomas Crooks wrote 'July 13 will be my premiere, watch as it unfolds' on gaming platform Steam before shooting the former president

Donald Trump's would-be assassin Thomas Matthew Crooks wrote an ominous warning on a gaming platform before he shot the former president.

DailyMail.com confirmed U.S. Senators were told the 20-year-old gunman posted on Steam: 'July 13 will be my premiere, watch as it unfolds.'

On July 13 he opened fire on the Republican nominee from a roof just 130 yards away from the rally stage in Butler, Pennsylvania.

Senators were also briefed that investigators found searches for Trump, President Joe Biden, when is the Democratic National Convention.

He also looked up more information about the July 13 rally where he carried out the horrifying attempt on the president's life.

The FBI also found he had two cell phones, the second of which was found at home with only 27 contacts. 

Senators also learned that Crooks was spotted by Secret Service 10 minutes before he walked out onstage - a full 20 minutes before he was shot.

Sources on the call told DailyMail.com that over an hour passed from the shooter being spotted to his initial shot. Even more troubling, Secret Service counter snipers saw Crooks on the roof 20 minutes before he shot the former president.

At 5:52 p.m. the 'suspicious' shooter was spotted on the roof by counter snipers. 

Trump walked out onto the stage at 6:02 p.m. 

Then at around 6:12 p.m. Crooks' first shots rang out.  

'That is a crazy amount of time they let pass before firing,' the source said. 

Sen. Mike Lee, R-Utah, confirmed this in a tweet Wednesday afternoon.

'They had identified the shooter as 'suspicious' a full 19 minutes before the shooting,' he posted. 

Lee said that senators were only allowed to ask four questions during the briefing, which he described as 'arbitrarily cut the call short.' 

Adding insult to actual injury, the officials in the briefing did not provide any information about why their response took so long. 

Secret Service Director Kimberly Cheatle did not know how Crooks got onto the roof, the source added. 

Also coming into question on the call was the possible motive for Crooks to commit such an atrocity. 

Officials did not confirm an operating motive and said that his rationale remains a mystery. 

They said that they have yet to find any ideological material that could shine light on why Crooks decided to shoot the former president.

But, they did reveal that Crooks operated several accounts on encrypted platforms that they are still working to gain access to, the source said. 

'He was identified as a character of suspicion because [he had] a rangefinder as well as a backpack. And this was over an hour before the shooting actually occurred,' Sen. John Barrasso, R-Wyo., said on Fox News Wednesday afternoon.

'So, you would think over the course of that hour, you shouldn't lose sight of the individual.'

'Somebody ought to be following up on those sorts of things. No evidence of that happening at all.'

The Wyoming Republican later posted a statement calling the meeting a '100 percent cover-your-a** briefing.'