A suspect in the shooting at the DNC office in Arizona was seen posting signs with bags of a white, powdery substance, officials say

(CNN) – Arizona investigators monitoring the man accused of shooting at the Democratic National Committee office in suburban Phoenix saw him posting political signs with bags containing a white, powdery substance attached, officials said .

Investigators in Tempe began monitoring 60-year-old Jeffrey Michael Kelly as a suspect in three separate shootings at the DNC office after receiving tips from the public, Tempe Police Chief Kenneth McCoy said at a news conference Wednesday.

They watched as Kelly placed the signs with the bags attached from late Monday through Tuesday morning, the chief said.

Kelly was arrested Tuesday and is being held on three counts of terrorist acts and four other charges related to the shooting.

He is being held on a $500,000 cash bond and will be placed on electronic monitoring if he is able to post that amount, Maricopa County Attorney Rachel Mitchell said at the news conference.

Kelly could face additional charges related to the powdered substance, McCoy said. It was not immediately known what substance was involved.

Arizona is among the crucial battleground states in the upcoming election, where the rivalry between Vice President Kamala Harris and former President Donald Trump has heated up. The campaign season has already been marked by violence, including alleged assassination attempts against Trump during a rally in Pennsylvania and at his golf course in Florida.

Kelly is accused of shooting three times at the DNC office in Tempe.

First, just after midnight on Sept. 16, Kelly fired more than 10 shots from a pellet gun into the front doors and windows of the building, McCoy said.

A week later, around the same time on Sept. 23, about six shots were fired into the building, damaging the front windows and office signs, the chief said.

“This time the situation escalated with the use of real bullets,” McCoy said.

Surveillance video from the second incident showed a silver Toyota SUV leaving the parking lot shortly after the shooting.

Two weeks later, just after midnight on Oct. 6, a glass break alarm went off and responding officers found three bullet holes in the front of the building, McCoy said.

The same silver SUV was seen in surveillance video, the chief said.

“Threats, intimidation or violence against political officials, regardless of party, are completely unacceptable,” Mitchell said. “These actions incite fear and undermine confidence in our elections, and frankly, they weaken our democratic system.”

“Our department recognizes the significance of this arrest and we want to assure our community that we are committed to ensuring you are safe as you go to the polls over the next 13 days,” McCoy said, denouncing political violence.

More than 120 guns and more than 250,000 rounds of ammunition were found in Kelly’s home after his arrest, prosecutors said at Kelly’s first court appearance Wednesday.

Investigators believe he may have planned a mass casualty event, prosecutors said.

“Of course … both the number of weapons and the number of cartridges are certainly a factor that you would consider,” Mitchell said at the news conference.

Kelly was suspected of stealing political signs in 2022, but “I don’t believe any charges were filed against him at that time,” McCoy said.

A review of Kelly’s Facebook posts found a large number of posts and memes that criticized liberals and Democrats, expressed support for former President Trump, and included pro-gun and military content dating back to 2012. After August 2023, there will be no more public posts on his site.

“We are continuing our investigation to find out if he had any other plans,” McCoy said.

“Anyone who engages in political violence or attempts to interfere in elections or prevent people from participating in the political process will face serious legal consequences. We will aggressively pursue law enforcement to protect our democracy and our democratic process,” Mitchell said.

The Arizona Democratic Party remains “undeterred and continues its work to ensure East Valley voters turn out in full force now through Election Day,” a spokesman for the group said.

Correction: An earlier version of this story incorrectly stated the suspect’s first name. His name is Jeffrey Michael Kelly.

CNN’s David Williams contributed to this report.