Protesters -- some of whom wore bandanas over their faces and carried Mexican flags -- blocked off the road in front of the Hyatt Regency here, forcing the GOP front-runner's motorcade to pull over along a concrete median outside the hotel's back entrance. Trump and his entourage got out and walked into the building.
"That was not the easiest entrance I've ever made," Trump said once he began speaking at the convention, adding, "it felt like I was crossing the border."
He slammed the protestors on Twitter Saturday, calling them "thugs and criminals."
"Many are professionals," he said. "They should be dealt with strongly by law enforcement!"
At one point before Trump arrived, about two dozen protesters tried to rush barriers near the hotel. Police officers then rushed to the building's doors, successfully blocking the protesters from getting in. Some of the doors' handles were handcuffed from the inside so they couldn't be forced open.
Several physical altercations, including shoving, could be seen between protesters and police officers, who were using batons to push them back.
After Trump arrived, protesters took down a barrier and flooded the entrance outside the hotel, where police again blocked them from entering. They chanted, "Get him out."
Earlier in the day, Chris Conway, a 51-year-old Trump supporter who was wearing the GOP front-runner's famous "Make America Great Again" cap, claimed he was kicked, punched and spit on by Trump protesters, though he wasn't seeking medical attention. Police, apparently concerned for his safety, eventually pulled him over hedges outside the hotel and away from the crowd.
Speaking to CNN Friday afternoon, Conway said he was "not surprised" by his treatment.
"To be honest with you, I'm glad it was me and not like an 8-year-old girl being pepper-sprayed or something like that," he said.
Burlingame Police Lt. Jay Kiely said later Friday that five people were arrested, including one who was with the crowd when it tried to rush the Hyatt's entrance. One injury was reported, but Kiely did not know whether it was a police officer, protester or supporter who was hurt or the extent of the injury.
Kiely estimated the crowd was in the hundreds, though he did not have a precise figure and did not know how many police officers were dispatched to the scene. He also praised the "incredible restraint" shown by authorities.
Outrage over Trump's immigration rhetoric
Protesters have disrupted Trump's rallies across the country for months, but have rarely escalated into mass street demonstrations. Many protests have focused on Trump's rhetoric on illegal immigration.
"I came out here to support my people and my father," Adrian Olivares, a 23-year-old college student who was draped in a Mexican flag, told CNN. He said his goal in protesting Trump's appearance was to display his country's flag "as loud as I can."
Olivares said his father came to the United States legally in the 1980s, became a citizen and created a home cleaning business in Sonoma County.
"He's very successful," Olivares said. "And for Trump to come out and say we're just a bunch of rapists, f--- him."
Frank Lara, 30, a fourth-grade teacher in San Francisco, brought a Trump pinata with him. He said he was most concerned about Trump's comments on immigration.
"We're upset at the hate speech and division that this man, Donald Trump, is saying in a time of crisis," Lara said. "We're out here to make sure that he does not feel comfortable just saying what he is saying."
Meanwhile, inside the hotel, a few dozen convention-goers and journalists watched the chaotic scene through the front windows, but otherwise most people hardly noticed. Instead, they perused convention exhibits or waited in line for the luncheon. Even as a group of police in riot gear suddenly sprinted through a long hallway, people continued to go about their business.
Richard Marshall, GOP chairman for Siskiyou County, was calmly strolling around in the hotel atrium and talking to friends, unfazed by the protesters who were trying to storm the entrance just feet away.
"It's part of the business, isn't it?" Marshall said. "I mean, I think it's unfortunate they don't want to have freedom of speech for everybody and want to have it all for themselves."
Earlier Friday, bare-breasted protesters, men and women, some of whom were associated with the progressive group Code Pink, chanted "stop hate" as they marched.
Nancy Mancias, a Code Pink protester, was kicked out of the convention after yelling into a bullhorn that the Republicans should "dump Trump," causing a stir inside the already energized state convention.
Mancias told CNN afterward, "My message here today is 'Stop hate and dump Trump.'"
The protests follow a rowdy scene
Thursday night outside Trump's rally in Costa Mesa, California, where several scuffles broke out between protesters and Trump supporters. At least one police car was damaged and one Trump supporter was visibly bloodied after being punched in the face.
About 20 people were arrested Thursday night, police said.
Trump calls for party unity
In his speech at the convention, Trump predicted the primary season would soon come to a close and called for Republicans to come together, stressing, "there has to be unity in our party."
But, he made sure to note, he could still win in November even if he fails to unite the party.
"Could I win without it? I think so, to be honest, I think so," he said. High-profile Republicans such as Jeb Bush, he continued, may not support him in the general, but he brushed that off as a minor issue. "Big deal, like I care. OK?"
"Again, ideally, we're going to be together," Trump said. "I think I will win even if we're not together. I mean there are some people, I honestly don't want their endorsement. I just don't want it ... It's not going to have any impact on whether or not we beat Hillary Clinton. It's not going to have any impact. But most of the party has to come together."
As he wrapped up his speech, Trump again mentioned the protests outside and the lengths to which he had to go to be there Friday afternoon.
"You have no idea the route they have planned for me to get out of here," Trump said.