TV Guide explains:
Did Andrew fire a warning shot for the man who came looking inside the
houseboat?
Yes. The man in charge of watching over the houseboat — which by the
way belonged to a man who ran gay bathhouses in Las Vegas and is
believed to be a place Andrew knew he could hide — alerted authorities
when he went to check on it and noticed the front door was
compromised. "His suspicions mounted as he and his wife entered,
because all the lights were on and the drapes, which were always open,
were drawn," Vulgar Favors says. Cushions had been pulled off the sofa
and made into a bed on the floor with a blanket, and a chair had been
turned over as if to form a barricade. As he pulled out his gun, he
heard a loud shot from the second-floor master bedroom. He and his
wife ran outside and hid in the bushes and he called his son, who
called the police.
Vulgar Favors is the book the series is based on:
Though the Versace family contends FX's series is fictitious, the
series is based on the book Vulgar Favors by investigative journalist
Maureen Orth — a Vanity Fair correspondent who spoke to more than 400
people in researching her exhaustively detailed book.