“Heavily armed” Oath Keepers arrived in Ferguson, Missouri, early Tuesday as protests marking the one-year anniversary of Michael Brown's death continued, albeit on a smaller scale, for a fourth consecutive night Monday.

The presence of members of the Oath Keepers organization -- which is made up "current and formerly serving military, police, and first responders" who “defend the Constitution against all enemies, foreign and domestic” -- was approved by local police but were instructed not to walk through police lines, according to a Guardian reporter.

Early Tuesday, the number of protesters in Ferguson had significantly diminished along West Florissant Avenue, with about 150 protesters reportedly seen along several blocks amid reduced police presence. Earlier in the day, about two dozen people were arrested in the area amid reports of bottles and other projectiles being thrown at police.

Meanwhile, the unrest in Ferguson reportedly forced Fox TV to cancel its “Empire” bus tour that was scheduled for Tuesday and Wednesday in St. Louis. The studio-equipped bus is traveling across the country conducting a contest that allows singers to audition for a guest appearance on the hit TV show.

On Monday, police arrested nearly 120 people, including about 60 demonstrators who were detained after blocking rush-hour traffic on Interstate 70. Protesters took to the streets during the night under a state of emergency in the St. Louis suburb, which is witnessing renewed protests over the death of the 18-year-old unarmed black teen who was shot by white officer Darren Wilson on Aug. 9, 2014. St. Louis County Police reported that frozen water bottles were thrown at police as clashes between law enforcement officials and protesters intensified.

St. Louis County police also said late Monday that a girl detained by police who media reported as aged 12 is actually 18, but did not give the reason for her arrest. Several prominent leaders from the Black Lives Matter organization and human rights activists were arrested early Monday but were later released.

Protests, which began Sunday, started off peacefully but turned violent in the late hours of Sunday and early Monday. Tensions escalated after an 18-year-old friend of Brown, Tyrone Harris Jr., was shot by police Sunday night. He has been charged with four counts of assault on law enforcement in the first degree, five counts of armed criminal action and one count of discharging or shooting a firearm at a motor vehicle and is currently being held on $250,000 cash-only bond.