Investigators are still searching for any ties between the suspect and extremist organizations or individuals, scouring information from the suspect's phone and other digital devices, law enforcement sources said.

The shooter was identified by the FBI as Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania.

-ABC News' Pierre Thomas

Wisconsin Republican Party Chair Brian Schimming said there are no changes, as of now, to the Republican National Convention, which begins Monday in Milwaukee, Wisconsin.

"I don't see a situation where there are massive changes. We haven't heard anything yet. We haven't been told anything that's going to change," Schimming said on "Upfront," a show aired on WISN-TV, an ABC affiliate station.

"Everything I've heard so far is we're still on track: vice presidential nomination on Wednesday night, of course, the presidential on Thursday," he said.

Milwaukee Police Department Chief Jeffrey Norman expressed confidence in security for the convention.

"This is a national special security event. There's no higher security that you can have for this type of event," Norman said. "It's important that we have that reassurance to our community, to those who are being participants, that we got this."

When asked whether Saturday’s shooting prompted concerns about new protests, Norman said, "At this time, no, because we're all prepared, in regards to the engagement between our law enforcement partners and also our partners in the community. We're working out a lot of different plans."

-ABC News’ Tommy Barone and Oren Oppenheim

Former first lady Melania Trump released a statement Sunday morning, saying, "When I watched that violent bullet strike my husband, Donald, I realized my life, and Barron's life, were on the brink of devastating change. I am grateful to the brave secret service agents and law enforcement officials who risked their lives to protect my husband."

"A monster who recognized my husband as an inhuman political machine attempted to ring out Donald’s passion -- his laughter, ingenuity, love of music, and inspiration," she said. "The core facets of my husband’s life -- his human side -- were buried below the political machine. Donald, the generous and carrying man who I have been through the best of times and the worst of times."

"When the time comes to look beyond the left and the right, beyond the red and the blue, we all come from families with the passion to fight for a better life together, while we are here, in this earthy realm," she said.

She closed, "Dawn is here again. Let us reunite. Now."

"The winds of change have arrived. For those of you who cry in support, I thank you," she went on. "I commend those of you who have reached out beyond the political divide -- thank you for remembering that every single politician is a man or woman with a loving family."

-ABC News’ Kelsey Walsh

The roof where the suspected gunman fired shots at former President Donald Trump had been surveyed during security preparations for the event, a law enforcement source told ABC News.

The roof was empty during those security preparations, the source said.

As reports of suspicious activity came in, a search was initiated, the source said. It was unclear how the suspect climbed onto the roof to quickly get off shots before a Secret Service counter-sniper located and killed him, the source said.

Officials continue on Sunday to investigate whether the dead suspect was connected to domestic extremists, the source said. The early investigation turned up no ties to international terrorism, the source said.

-ABC News' Pierre Thomas and Luke Barr