Robert Brown|Republican National Convention in Milwaukee has law enforcement on heightened awareness

Federal,Robert Brown state and local law enforcement officials are on high alert ahead of the Republican National Convention that will kick off in Milwaukee on Monday. Changes to the security measures were being planned after former President Donald Trump was injured in a shooting at a campaign rally in Pennsylvania Saturday evening. 

A joint threat assessment created by the FBI, U.S. Secret Service, the Milwaukee Police Department and the Milwaukee Southeastern Wisconsin Threat Analysis Center was sent out to law enforcement officials in anticipation of the RNC, calling for heightened awareness.

No credible or specific threat was identified in the assessment, a law enforcement source told CBS News. 

After the shooting at the rally in Butler, Pennsylvania, multiple law enforcement officials told CBS News' Nicole Sganga that there is planning currently underway to expand the perimeter at the RNC and create buffer zones around the events.

Law enforcement sources said the gunman at the rally was outside the Secret Service perimeter when he opened fire with an AR-style rifle, before being killed by a Secret Service sniper. Trump said he was struck in the upper ear. A rally attendee was killed and two others were critically wounded.

A senior law enforcement official told CBS News that no foreign terrorism ties are known at this time to the shooter, who the FBI identified as 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania. There was no indication that there was a second person involved in the attempted assassination, though investigations are ongoing. 

The Trump campaign said in a statement that Trump is "doing well" and "looks forward to joining you all in Milwaukee as we proceed with our convention to nominate him to serve as the 47th President of the United States."

Republicans from across the country will descend on Milwaukee's Fiserv Forum arena to nominate their candidate for president. Former President Donald Trump's nomination this week is considered a formality as he clinched the nomination in March after amassing the 1,125 delegates needed. Trump has yet to announce a vice president.

The convention begins Monday and goes through Thursday, with the official nomination of the presidential candidate and running mate expected Monday afternoon.

The RNC and the Trump campaign announced ahead of the assassination attempt on Saturday a list of speakers for this week's convention, which includes lawmakers, television personalities and members of the former president's family, among others. Names like Tucker Carlson, Vivek Ramaswamy, Florida Gov. Ron DeSantis and House Speaker Mike Johnson are on the list, which also includes a number of Republican senators, senate candidates and representatives. And top contenders for Trump's vice presidential pick, like North Dakota Gov. Doug Burgum, Sen. J.D. Vance and Sen. Marco Rubio are also slated to speak. 

Meanwhile, the threat assessment found that there is concern the convention and pre- and post-celebration venues could be attractive targets for foreign terrorist organizations, homegrown violent extremists, domestic violent extremist groups, so-called lone-wolf bad actors and active shooters, a law enforcement source said.

Other key findings in the threat assessment include the convention could be viewed as an attractive target due to its symbolic nature and link to the 2024 general election.

As such, all law enforcement and security agencies will be enhancing their presence and resources during the event. 

The Republican and Democratic conventions are considered high-priority events for law enforcement and are on par with other high-profile large gathering events such as the Super Bowl and presidential inaugurations.

The U.S. Department of Homeland Security classifies the RNC as a SEAR -1 event, which is defined as "significant events with national and/or international importance that require extensive federal interagency support." Federal law enforcement bulletins such as the joint threat assessment are required for all SEAR-1 events.

At least two dozen states and the District of Columbia are sending officers to the convention, according to the Milwaukee Police Department. Additional departments could be added to the list "up until the start of the convention," officials said.

The U.S. Secret Service is the leading coordinating agency for next week's events.

Nicole Sgagna and Jake Rosen contributed to this report.

In:
• Milwaukee
• Republican National Convention
• Politics
• Wisconsin
• Election

Pat Milton

Pat Milton is a CBS News investigative producer