(CNN) At what was his largest campaign event yet -- with a huge U.S. flag stretched from one side of the stage to the other -- Donald Trump addressed his faithful followers Saturday at the Phoenix Convention Center.

Two dozen supporters stood behind the Republican presidential candidate holding signs reading, "Trump, Make America Great Again," while an estimated 5,000 supporters looked on.

Expressing his amazement at the size of the crowd, Trump said, "This is unbelievable. This began as 500 people in a ballroom in Phoenix."

The campaign was asked to move to a larger venue to accommodate the thousands of people who wanted tickets, according to Trump spokeswoman Hope Hicks.

The Trump campaign said 15,000 tickets were distributed for the event at the Phoenix Convention Center, where the North Ballroom has a capacity of only 4,200, according to the facility's website. The campaign said thousands were turned away because of fire regulations.

The candidate was welcomed by several high-profile supporters, including Maricopa County Sheriff Joe Arpaio, whose stands against illegal immigration and often controversial punishments have earned him a reputation as a hard-nosed, unyielding lawman.

During his speech, Trump turned the lectern over to Jamiel Shaw Sr., the father of a high school student killed by an undocumented immigrant, who spoke about why he is supporting the candidate.

Although campaign aides said earlier Saturday that Shaw was going to introduce the candidate, he ended up speaking midway through the speech.

Shaw's son, a high school football star, was shot and killed in Los Angeles in 2008 by a gang member born in Mexico. On Friday , Trump met in Los Angeles with Shaw and other family members of victims of crimes perpetrated by undocumented immigrants. He then gave a lengthy press conference in which he consistently railed against illegal immigration. Saturday's speech was filled with similar words.

Brief disturbance

Playing to the crowd, Trump dug in on the controversial themes that have made him loved by some and despised by others. As he mentioned earlier in the day at a Las Vegas campaign rally, Trump claimed China is laughing at U.S. trade negotiations. "They have geniuses and we have people who don't have a clue. We have stupid leaders," he said.

Trump, who announced his White House campaign bid last month, sparked national outrage by saying that some people crossing the border into the United States from Mexico were "rapists" and "criminals." A slew of corporations, including Macy's, NBC and ESPN, responded to his inflammatory remarks by severing business ties with the real estate magnate.

"I love the Mexican people," he said. "I love their spirit. I respect Mexico as a country. Their leaders are much sharper and smarter than ours."

But, Trump said, "They're killing us at the border and killing us in trade."

Photos: Donald Trump's rise Photos: Donald Trump's rise President-elect Donald Trump has been in the spotlight for years. From developing real estate and producing and starring in TV shows, he became a celebrity long before winning the White House. Hide Caption 1 of 37 Photos: Donald Trump's rise Trump at age 4. He was born in 1946 to Fred and Mary Trump in New York City. His father was a real estate developer. Hide Caption 2 of 37 Photos: Donald Trump's rise Trump, left, in a family photo. He was the second-youngest of five children. Hide Caption 3 of 37 Photos: Donald Trump's rise Trump, center, stands at attention during his senior year at the New York Military Academy in 1964. Hide Caption 4 of 37 Photos: Donald Trump's rise Trump, center, wears a baseball uniform at the New York Military Academy in 1964. After he graduated from the boarding school, he went to college. He started at Fordham University before transferring and later graduating from the Wharton School, the University of Pennsylvania's business school. Hide Caption 5 of 37 Photos: Donald Trump's rise Trump stands with Alfred Eisenpreis, New York's economic development administrator, in 1976 while they look at a sketch of a new 1,400-room renovation project of the Commodore Hotel. After graduating college in 1968, Trump worked with his father on developments in Queens and Brooklyn before purchasing or building multiple properties in New York and Atlantic City, New Jersey. Those properties included Trump Tower in New York and Trump Plaza and multiple casinos in Atlantic City. Hide Caption 6 of 37 Photos: Donald Trump's rise Trump attends an event to mark the start of construction of the New York Convention Center in 1979. Hide Caption 7 of 37 Photos: Donald Trump's rise Trump wears a hard hat at the Trump Tower construction site in New York in 1980. Hide Caption 8 of 37 Photos: Donald Trump's rise Trump was married to Ivana Zelnicek Trump from 1977 to 1990, when they divorced. They had three children together: Donald Jr., Ivanka and Eric. Hide Caption 9 of 37 Photos: Donald Trump's rise The Trump family, circa 1986. Hide Caption 10 of 37 Photos: Donald Trump's rise Trump uses his personal helicopter to get around New York in 1987. Hide Caption 11 of 37 Photos: Donald Trump's rise Trump stands in the atrium of the Trump Tower. Hide Caption 12 of 37 Photos: Donald Trump's rise Trump attends the opening of his new Atlantic City casino, the Taj Mahal, in 1989. Hide Caption 13 of 37 Photos: Donald Trump's rise Trump signs his second book, "Trump: Surviving at the Top," in 1990. Trump has published at least 16 other books, including "The Art of the Deal" and "The America We Deserve." Hide Caption 14 of 37 Photos: Donald Trump's rise Trump and singer Michael Jackson pose for a photo before traveling to visit Ryan White, a young child with AIDS, in 1990. Hide Caption 15 of 37 Photos: Donald Trump's rise Trump dips his second wife, Marla Maples, after the couple married in a private ceremony in New York in December 1993. The couple divorced in 1999 and had one daughter together, Tiffany. Hide Caption 16 of 37 Photos: Donald Trump's rise Trump putts a golf ball in his New York office in 1998. Hide Caption 17 of 37 Photos: Donald Trump's rise An advertisement for the television show "The Apprentice" hangs at Trump Tower in 2004. The show launched in January of that year. In January 2008, the show returned as "Celebrity Apprentice." Hide Caption 18 of 37 Photos: Donald Trump's rise A 12-inch talking Trump doll is on display at a toy store in New York in September 2004. Hide Caption 19 of 37 Photos: Donald Trump's rise Trump attends a news conference in 2005 that announced the establishment of Trump University. From 2005 until it closed in 2010, Trump University had about 10,000 people sign up for a program that promised success in real estate. Three separate lawsuits -- two class-action suits filed in California and one filed by New York's attorney general -- argued that the program was mired in fraud and deception. Trump's camp rejected the suits' claims as "baseless." And Trump has charged that the New York case against him is politically motivated. Hide Caption 20 of 37 Photos: Donald Trump's rise Trump attends the U.S. Open tennis tournament with his third wife, Melania Knauss-Trump, and their son, Barron, in 2006. Trump and Knauss married in 2005. Hide Caption 21 of 37 Photos: Donald Trump's rise Trump wrestles with "Stone Cold" Steve Austin at WrestleMania in 2007. Trump has close ties with the WWE and its CEO, Vince McMahon. Hide Caption 22 of 37 Photos: Donald Trump's rise For "The Apprentice," Trump was honored with a star on the Hollywood Walk of Fame in January 2007. Hide Caption 23 of 37 Photos: Donald Trump's rise Trump appears on the set of "The Celebrity Apprentice" with two of his children -- Donald Jr. and Ivanka -- in 2009. Hide Caption 24 of 37 Photos: Donald Trump's rise Trump poses with Miss Universe contestants in 2011. Trump had been executive producer of the Miss Universe, Miss USA and Miss Teen USA pageants since 1996. Hide Caption 25 of 37 Photos: Donald Trump's rise In 2012, Trump announces his endorsement of Republican presidential candidate Mitt Romney. Hide Caption 26 of 37 Photos: Donald Trump's rise Trump speaks in Sarasota, Florida, after accepting the Statesman of the Year Award at the Sarasota GOP dinner in August 2012. It was shortly before the Republican National Convention in nearby Tampa. Hide Caption 27 of 37 Photos: Donald Trump's rise Trump appears on stage with singer Nick Jonas and television personality Giuliana Rancic during the 2013 Miss USA pageant. Hide Caption 28 of 37 Photos: Donald Trump's rise In June 2015, during a speech from Trump Tower, Trump announced that he was running for President. He said he would give up "The Apprentice" to run. Hide Caption 29 of 37 Photos: Donald Trump's rise Trump -- flanked by U.S. Sens. Marco Rubio, left, and Ted Cruz -- speaks during a CNN debate in Miami on March 10. Trump dominated the GOP primaries and emerged as the presumptive nominee in May. Hide Caption 30 of 37 Photos: Donald Trump's rise The Trump family poses for a photo in New York in April. Hide Caption 31 of 37 Photos: Donald Trump's rise Trump speaks during a campaign event in Evansville, Indiana, on April 28. After Trump won the Indiana primary, his last two competitors dropped out of the GOP race. Hide Caption 32 of 37 Photos: Donald Trump's rise Trump delivers a speech at the Republican National Convention in July, accepting the party's nomination for President. "I have had a truly great life in business," he said. "But now, my sole and exclusive mission is to go to work for our country -- to go to work for you. It's time to deliver a victory for the American people." Hide Caption 33 of 37 Photos: Donald Trump's rise Trump faces Democratic nominee Hillary Clinton in the first presidential debate, which took place in Hempstead, New York, in September. Hide Caption 34 of 37 Photos: Donald Trump's rise Trump apologizes in a video, posted to his Twitter account in October, for vulgar and sexually aggressive remarks he made a decade ago regarding women. "I said it, I was wrong and I apologize," Trump said, referring to lewd comments he made during a previously unaired taping of "Access Hollywood." Multiple Republican leaders rescinded their endorsements of Trump after the footage was released. Hide Caption 35 of 37 Photos: Donald Trump's rise Trump walks on stage with his family after he was declared the election winner on November 9. "Ours was not a campaign, but rather, an incredible and great movement," he told his supporters in New York. Hide Caption 36 of 37 Photos: Donald Trump's rise Trump is joined by his family as he is sworn in as President on January 20. Hide Caption 37 of 37

Trump also promised to release financial documents next week that will show he is an even more successful businessman than has been reported.

"I'm not saying that to brag," he said.

A short protest broke out during the speech. Some protesters held up a banner and Trump supporters started screaming at them. It was unclear what the banner read.

There was a brief scuffle and for a few minutes it was very tense. Security came and escorted the protesters out.

"I wonder if the Mexican government sent them over here," Trump said.

"Don't worry, we'll take our country back," he said, as the crowd cheered.

'He can inspire a crowd'

Robert Bowater said he came to see Trump in Phoenix because he thinks the issues of illegal immigration and sanctuary cities deserve more attention.

Bowater, a 68-year-old resident of Pinal County, Arizona, said he doesn't expect any President to deport all undocumented immigrants, but he thinks more can be done to punish the ones who commit crimes in the United States.

"I'd like to see a mass deportation of the criminals," Bowater said.

Just as Bowater was saying he thought it was possible that Trump could win the presidency, Linda Murtha -- standing behind him -- couldn't help but shake her head.

"He can't win," said Murtha, a Chandler resident in her early 40s, but "he definitely can inspire a crowd."

She came to the event with her mother, Provi Murtha, who was interested in seeing "The Donald" in person. Like her daughter, Provi is skeptical of Trump's intentions. She noted that he's donated to Democrats, including Hillary Clinton.

"Is he a Democrat? Is he a Republican? What is he?" Provi wondered aloud. Even though she came to see the event, "I'm not going to make up my mind to vote for Donald Trump, that's for sure."

Both Provi and Linda Murtha said they like Kentucky Sen. Rand Paul.

Freedom Fest warm-up

In a warm-up to his appearance at the Phoenix campaign rally, Trump stopped by Freedom Fest in Las Vegas, an annual gathering of conservatives, where he addressed a crowd of several hundred people and took questions.

But first he called Shaw to the stage. The room was hushed as Shaw talked about his son who was gunned down seven years ago by an undocumented immigrant. Shaw said the man who killed his son had been released from a county jail on his third gun charge, four months early. His son was walking home, and was close enough for Shaw to hear the gunshots.

Shaw said he almost thinks of Trump "as a father figure" even though the two are similar in age. "He's the kind of man you would want to be your dad," Shaw said. "He's a nice guy. He put himself out there for black people. I know I can trust him," Shaw continued.

He said when Trump spoke out about illegal immigration he saw that "Trump loves America" and is willing to risk his life for it.

Trump doubles down -- again

Trump doubled down once more on comments that have ignited a controversy in the United States

Illegal immigration is "a major, major problem in this country" that has to be solved, Trump said.

Promising to secure U.S. borders with a impenetrable fence, Trump claimed undocumented immigrants are coming to the United States from all over the world. "This isn't just Mexico," he said. "They're coming from the Middle East, and we better be very careful," Trump warned.

And the support that he is receiving from Shaw and others demonstrates that the businessman's message is appealing to some voters who view illegal immigration as a serious problem.

On the subject of trade, Trump was blunt with his opinion of U.S. trade negotiators, "Chinese leaders are much smarter than (President Barack) Obama and his bunch of clowns," he said to laughter and applause from crowd.

"I make good deals. I have great respect for China. Their leaders are too smart for our leaders," he said.

Trump fervor increasing

Trump's fervor appears to increase with each campaign rally as he ramps up his rhetoric against illegal immigration.

Detractors are many, including some in his own party, but Trump is gaining supporters as well -- evidenced by the switch in venues for Saturday's event to the Phoenix Convention Center. Trump tweeted Saturday night that he would not be attending the Miss USA Pageant in Baton Rouge, Louisiana, on Sunday because he had campaign stops scheduled in Phoenix. Trump is a partial owner of the Miss Universe Organization, which oversees the pageant.

A CNN/ORC poll released July 1 found Trump and Republican rival, former Florida Gov. Jeb Bush, on the rise nationally.

The two are the only GOP presidential contenders to enjoy double-digit support among Republicans and Republican-leaning independents.