You don't have a right to detain someone if you haven't witnessed them commit a crime. Trespassing on a construction site isn't a felony, call the police.
"The initial handling of the case by law enforcement also made headlines. Former Glynn County District Attorney Jackie Johnson
was indicted in September for alleged misconduct, after allegedly telling two police officers not to arrest Travis McMichael and obstructing another officer. The case was ultimately transferred to four different prosecutors’ offices, and the McMichaels were not arrested until May 7, 2020, more than two months after the killing. Bryan was arrested on May 21, 2020."