The US national anthem rang out. Scores chanted "USA! USA!" And among the handmade signs, the demand: "Return to sender."
Protesters in the small California town of Murrieta are fighting what they say is an "invasion" of illegal immigrants. The demonstrators turned up a week ago at this US Border Patrol facility for detained migrants, and, vowed Greg Allison, "we're not going anywhere."
Last week, a rambunctious group blocked three buses transporting 140 migrant women and children. Now they are ready to do it again.
"It's the third time I'm making the trip from San Diego in one week," said Dan Russell, 71.
A retiree sporting a black t-shirt with a menacing-looking eagle under the word "America," Russell said he had come back because "we heard on the radio that another bus was coming."
Other protesters carried flags and handmade signs reading "Remember 911 and Benghazi," "Where are the dollars for our vets?" "We want a fence not a reform," and "It's not about hate. It's about love for our own."
Allison, who is unemployed, railed against "the federal government" which he said was "dumping illegal immigrants here" and calling it "humanitarian."
Overwhelmed by the massive waves of mostly lone child immigrants crossing from Mexico into Texas and Arizona, the US government has been forced to transfer some of them to detention centers elsewhere, including in California.
It is part of a wider -- and often bitter -- debate in the US about immigration.
Murrieta residents fear that, after submitting the children to medical tests and legal processing, authorities will let them free to roam the town.
"Why not have all the oppressed children from Sudan or Ukraine or China come here as well?" Allison asked sarcastically.
"If we don't stop them we'll turn into a third world country," he warned, while by his side Heidi Blink exclaimed against the "invasion."
Russell lamented that "the frontier is wide open. Everybody can pass.
"They're bringing third world diseases," he said, citing "reports on polio and H1N1" flu virus.
"They should have been quarantined in Texas," a border state through which a large percentage of migrants pass, he insisted.
- 'See brown' -
US President Barack Obama is to visit Texas in the coming days, part of the high-level US response to the flood of undocumented children that officials have termed a humanitarian crisis and that has sparked a political firestorm.
More than 52,000 unaccompanied minors have been detained since October after crossing the border illegally, twice the number from the same period a year ago. Most come from Central America, fleeing poverty and violence in their home countries.
US Secretary of Homeland Security Jeh Johnson pledged Sunday the United States would "stem this tide," citing increased and speedier deportations.
But in Murrieta, the tide was not yet turned.
"We got some information this morning from the border patrol telling us a bus could come, but then we've learnt it had gone to San Ysidro," near San Diego, said Dennis Vrooman, of the Murrieta police.
Nevertheless, Vrooman said he and his team were ready to ensure the safe passages of any buses arriving in the coming days.
Monday's rallies were calm, but that was not the case over the July 4 holiday weekend, when several people were arrested after clashes between rival anti- and pro-immigration protests.
The pro-immigration camp was back out again on Monday, with one young demonstrator, Miguel Hernandez, defending the people who make the illegal trek.
"They are getting tortured" in their home countries, said the 20-year-old American, who was wearing a Mexico football jersey.
He blasted what he said was the racism of the anti-immigration protesters, who "see brown and they think it's not good."
But Hernandez said the immigrants will benefit the United States: "Once they get an education, these kids are gonna work hard. That's what people don't understand."